Planar-structure microscope-lens for simultaneous acoustic and optical imaging

A new type of combined acoustic and optical microscope lens with a planar structure is proposed. It can meet the demand for simultaneously obtaining both an acoustic image and its optical counterpart. The lens is composed by uniting a Fresnel-zone-type acoustic lens developed by the authors with a rod-type gradient-index optical lens (SELFOC). An acoustic beam is converged to a focal point in water by an acoustic planar lens that is composed of annular grooves formed on the end of the SELFOC rod. An optical beam, emitted by a He-Ne laser source and guided into the rod, converges due to the gradient of the refractive index and focuses on a spot in water. By designing the length of the rod properly, the focal spot of the optical beam is set to coincide with that of an acoustic beam. The design and fabrication of the lens are described, and results of some preliminary experiments for simultaneous observation of acoustic and optical images of the same portion of a specimen are shown.<>