[OPTICAL REVIEW Vol. 7, No. 2 (2000) 119-122]

Artifact Halo Reduction in Phase Contrast Microscopy Using Apodization

Tatsuro OTAKI

Optical Design Department, Instruments Company, Nikon Corporation, 471, Nagaodai-machi, Sakae-ku, Yokohama, Kanagawa, 244-8533 Japan

(Received October 18, 1999; Accepted January 24, 2000)

A new phase contrast microscopy technique for halo reduction is proposed. This technique is based on an apodization method combined with the Zernike phase contrast method. Although it has been a difficult theoretical problem, the proposed technique achieves halo reduction by considering angles of diffraction and phase differences. The technique utilizes an apodized phase plate consisting of a quarter wave phase shift ring with a 25% transmittance, and a pair of adjacent rings, which have 50% transmittance. This element is placed at the back focal plane of the objective. The result is startling, halo reduced images of phase objects providing enhanced inner details.

Key words : phase contrast microscopy, apodization, halo, apodized phase plate, angle of diffraction, phase difference, mass fractal, surface fractal, combined fractal, self-similarity, power law, fractal dimension