Abstract: Techniques are provided for illuminating a sample by using total internal reflection (TIR) from a diffraction limited focused annular illumination beam. The illumination forms an affected region and an overlapping confocal region that may have dimensions the below 1 ?m. An adjustable diffractive optical element, for example, may create a second order Bessel profile laser beam that is focused on a sample using a high-numerical aperture objective under TIR. An evanescent field excites fluorescent biological material in the confocal region, and fluorescence from the material is analyzed in fluorescence correlation spectroscopy system.

Abstract: Techniques are provided for illuminating a sample by using total internal reflection (TIR) from a diffraction limited focused annular illumination beam. The illumination forms an affected region and an overlapping confocal region that may have dimensions the below 1 ?m. An adjustable diffractive optical element, for example, may create a second order Bessel profile laser beam that is focused on a sample using a high-numerical aperture objective under TIR. An evanescent field excites fluorescent biological material in the confocal region, and fluorescence from the material is analyzed in fluorescence correlation spectroscopy system.

Abstract: A piezo-electric transducer for low frequency acoustical waves comprising a stack of piezo-electric elements and alternating electrodes disposed between a front receiver plate and a counter mass. The countermass comprises a rigid annular block surrounding the stack, a rear plate engaging the rear of the stack and an elastic connection between the block and the rear plate.