Acoustic microscope for analyzing an object in depth having aspherical lenses

Claim 1

An acoustic microscope permitting the analysis of an object in depth comprising two identical bars positioned in an extension of one another and provided at their facing ends with a cavity, said cavities defining at least one focussing lens and at least one objective lens, said two identical lenses having coinciding foci being linked by a liquid drop in which the object to be analysed can be immersed, the bars being provided at their other ends with a piezoelectric transducer, said transducers being able to produce ultrasonics focussed within the object by the focussing lens and to detect ultrasonics reflected or transmitted by the object via the objective lens, means for analysing the ultrasonics reflected or transmitted by the object and means for displacing the object in the focal plane of the two lenses, wherein the lenses have in each case a shape defined by the parametric equations: ##EQU3## in which N represents the relative refractive index n 2 /n 1 , n 1 being the index of the material forming the bars and n 2 the index of the liquid, n representing the relative refractive index n 3 /n 2 , in which n 3 is the index of the material forming the object, D represents the distance between the vertex of the lens and the surface of the object, a the distance between the surface of the object and the focal point of the lens and r the parameter, x being taken along the optical axis of the lens and y along the axis perpendicular to said optical axis.