We propose a 4Pi confocal system that incorporates a phase-conjugate mirror into the system to solve the alignment problem and automatically correct the spherical aberration associated with the conventional 4Pi confocal system when observing a thick sample. The proposed system is experimentally verified by use of cerium-doped barium titanate crystal as the phase-conjugate mirror. The full width of the central peak is ~0.15 µm. We also theoretically verify the advantage of automatic correction of the spherical aberration by calculating the intensity distribution at the focal spot.
© 1996 Optical Society of America
Y. Kawata, K. Fujita, O. Nakamura, and S. Kawata, "4Pi confocal optical system with phase conjugation," Opt. Lett. 21, 1415-1417 (1996)