U.S. Philips Corporation

Cornelis Martinus Van Der Burgt

Gerardus Andreas Van Maanen

For accurate measurements of the sound velocity in liquids, for example water, the propagation delay is measured between an ultrasonic wave which is emitted by a transducer and the wave which returns to the transducer upon reflection. By making the reflector spherical and disposing it at a distance from the transducer which is within 11/2 times the length of the Fresnel region of the emitted acoustic wave, a favorable ratio between the 1 .tau. and the 2 .tau. signal is obtained, which ratio can be further improved when the central portion of the reflector is slightly flattened.

Propagation delay meter

A voltage sensitive trigger circuit with a threshold which must be temperature and supply-voltage independent. To this end, a preamplifier is employed which in itself is not only provided with negative feedback but which also receives a current which is derived from that trigger transistor, which in the quiescent condition is conducting.

Voltage sensitive trigger circuit

Apparatus for the detection of an acoustic image by means of an election tube including a face plate and an electronically scanned transducer made of a thin foil of polymer material whose acoustic wave velocity of propagation is less than 1.8 that of a liquid imaging medium. The face plate also is made of a polymer material having a velocity of propagation less than 1.8 that of said liquid. Preferably, the transducer foil is much thinner than the face plate and has a thickness approximately 0.5 times the acoustic wavelength.

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Eindhoven, Netherlands

Cornelis Martinus Van Der Burgt