Precision measurement of acoustic reflectivity for a scanning acoustic microscope that measures amplitude and phase: Applicability in biology

摘要

Sundry image processing schemes for a high-frequency (1.2 GHz) scanning acoustic microscope that measures amplitude and phase are presented. Particular emphasis is paid to the acquisition of precise in-focus information, like the acoustic reflectivity, of three-dimensional microscopic objects. The brightness of a surface element of any object under observation depends not solely on the reflectivity. It is also affected by the tilt angle of the surface with respect to the axis of the microscope. Vector microscopy with synchronous observation of the phase and amplitude has been employed to determine the tilt from the image in phase contrast and correct the observed brightness in the image in amplitude contrast accordingly. Additionally three-dimensional scanning has been used to determine the maximum intensity obtained for confocal positioning of any surface element. The relevance of such schemes for truly quantitative measurements in biology is demonstrated, with results that have led to the ascertainment of phenotypic plasticity in daphnia (waterfleas) species.