The imaging of a dielectric microsphere with linearly polarized backscattered light is investigated theoretically. Analytical expressions for the electric field and the imaged light intensity distribution in two dimensions are obtained for an arbitrary backscatter geometry, including both telescopic and microscopic arrangements. These distributions are shown to be in many cases more sensitive to small variations in the refractive index of the imaged particle than those obtained by imaging in the off-axis scattering. In microscopic geometry, the sensitivity may be further enhanced by the secondary imaging of the glare rings formed by the backscattered peripheral rays. The possibility of using the backscatter imaging for the absorption spectroscopy of small impurities is discussed.
© 1997 Optical Society of AmericaPDF Article