Pyroelectric applications imaging devices

The development of pyroelectric thermal imaging devices is dependent upon the screening of suitable materials. The materials,which are most likely to find application, will have large values of pyroelectric coefficient,and small permittivity and dielectric loss. The ability to produce thin films of optimum thickness will also be significant. 

Pyroelectric ceramics can be used to detect any radiation that produces a change in the temperature of the crystal, but are generally used for IR detection. Because of their extreme sensitivity a rise in temperature of less than one-thousandth of a degree can be detected. This property finds application in devices such as intruder alarms, thermal imaging, and geographic mapping. 

The pyroelectric effect is well documented, and has been reported for a wide range of inorganic and organic materials [1]. One of the most promising applications of pyroelectricity is in the area of infra-red or thermal imaging. Thermal information from a scene is derived by measuring the pyroelectric currents from elements in an array onto which the scene has been projected. In order to optimise the performance of thermal imaging devices, it is necessary to be able to characterise pyroelectric materials,both in terms of their intrinsic properties,and their performance in m el systems. 

Pyroelectric devices convert changing incident thermal radiation to an electrical output, and are now much used in intruder detectors, thermal imaging systems etc. Conventionally, ceramics have been used in such applications however, considering the desirable properties of large pyroelectric coefficient, high volume resistivity, low dielectric constant and loss, and low specific heat, it can be seen that, apart from the rather low pyroelectric coefficient, polymeric materials are superior to ceramics in several respects. 

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