This letter describes the spectroscopic measurements of fluorescently stained cells. Variable phase-contrast fluorescence spectrometry was used on fluorescently stained cells to achieve high two-dimensional spatial resolution. Phase shift interferometry by autocorrelation interference made it possible to measure fluorescence spectra in the field of view without the separation of wavelengths, as in the case of a conventional dispersive spectrometer. In this letter, the authors describe the experimental characteristics of fluorescence spectra generated from fluorescently stained cells and verify that the fluorescence spectra of the stained area in the cells can be measured by our method.

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A precise method to rotate single cells is reported. In this method, the light pressure in the optical axis direction is harnessed as a rotating torque. Two proximal points in each cell are illuminated from different directions using two beams, and a light pressure is created that acts as a rotating torque. Using this proposed method, we could control the rotational direction of a microsphere regardless of the refractive index distribution in a noncontact operation. The microsphere could be rotated using proximal two-beam optical tweezers, and the rotational velocity could be controlled by changing the light intensity.

A three-dimensional phase-contrast imaging technique that does not involve fluorescent labeling has been developed for observing floating cells. In this method, a single floating cell is made to rotate and images are acquired at several orientations of the cell using a phase-contrast microscope. From these two-dimensional phase-contrast images, three-dimensional cross-sectional images are obtained using the conventional computed tomography algorithm. This proposed method enabled successful rotation of a floating cell (a breast cancer cell line) and reconstruction of three-dimensional phase-contrast images. In these reconstructed three-dimensional images, the distribution of cell organelles is obtained and the cell nucleus is clearly distinguishable.

Simple fiber-optic confocal microscopy with nanoscale depth resolution beyond the diffraction barrier Rev. Sci. Instrum. 78, 093703 (2007);