a method and apparatus for visualizing in three - dimensions an image of a subsurface object such as an internal structure of a mechanical component , or of a fetus or other internal biological feature within a human body , utilizes a sensor such as an ultrasonic transducer of an ultrasound wand to acquire ultrasonic images of an object , and a target plate attached to a wand which is optically imaged by a digital camera during each of a sequence of ultrasound scans . each ultrasound image scan of an object is made with the position and / or orientation of the ultrasonic scan beam changed , thereby forming a sequence of quasi two - dimensional slices which intersect the object at different locations and / or aspect angles . visual features of the target plate such as pairs of intersecting lines are used to calculate a first coordinate transformation which transforms each electronically recorded oblique optical image of the target plate and sensor to a normal view thereof , and each normally oriented target plate image is used to orient each sonogram image in a fixed coordinate system . a transformation matrix is then used to assemble in a fixed three - dimensional coordinate system a plurality of normalized two - dimensional sensor image slices of correct relative size , location , and orientation . the assembly of sensor image slices enables visualization of the object in three - dimensions , as for example by mentally constructing directrix lines between contour perimeters of adjacent normalized sensor image slices to thereby define a three - dimensional image surface of the object .