Apparatus for examining an object by means of ultrasonic waves

The apparatus comprises a cylindrical carrier (1) which is rotatable about a supporting shaft (5) and is provided with n transducers (3) regularly distributed around its periphery, a first display device (35) for the display of a circular sector scan ultrasonic image with m radial picture lines in the B-mode, and a second display device (37) for an M-mode display of an ultrasonic image which consists of images relating to a single selected picture line (k) of the former image relating to successive instants in time, the successive line images being arranged parallel to one another with the same interline spacing. In order to obtain a line image repetition frequency in the M-mode for the selected picture line (k), which is n times greater than the picture frequency in the B-mode, the device is arranged so that each of the n transducers provides data for the formation of a corresponding group of m/n picture lines during one revolution of the carrier, the transducers taken as a whole together providing the data for all m picture lines. The image is formed in the B-mode by an n-fold line interlace (e.g. FIG. 4 where n=4). Each time any one of the transducers is in a position to provide data concerning the selected picture line (k), the formation of the image in the B mode is interrupted, the relevant transducer is activated to form the selected picture line (k), and transmitter pulses relating to any of the (n-1) lines following the selected line in the numerical sequence of lines, is suppressed.