Performance of an Ultrasound Camera Tube Utilizing Pyroelectric Conversion Layers

Abstract

The Sokoloff type ultrasound camera tube uses a piezoelectric target as the basic ultrasound-to-charge pattern converting layer. The scanning beam interaction with the conversion surface is such that only the energy in the piezoelectric element during the time interval the scanning beam is touching that element is effective in forming the visual signal. This characteristic operation has precluded for all practical purposes the use of pulsed ultrasound radiation in systems utilizing the Sokoloff Tube.¹ The work reported here involves the use of an ultrasound sensitive pyroelectric target which provides image storage in the form of a spatial temperature differential related to the absorbed ultrasound energy. The signal output produced by the scanning beam is directly related to the stored temperature differential existing on the extended layer pyroelectric material which is produced by absorption of the ultrasound in the target material. It is only recently that highly sensitive pyroelectric materials in a readily managed form have become available.² The ability to store the incident ultrasound energy for subsequent scanning permits utilization of the advantageous duty cycle relationship with regard to the interaction of ultrasound with biological organisms.³ It should be emphasized that in this type of ultrasound camera tube the signal at each picture point is, under proper conditions, integrated continuously which serves to increase the efficiency of detection. The practical limitation on obtaining this idealized operation is set by the thermal loss associated with the supporting structure for the pyroelectric conversion layer.