(US4469943-A)      The detector includes an element of pyroelectric material having at least one pair of opposed faces for generating electrical charges when the temp. of the element changes. An electrode extends over at least one of the faces of the pair for detecting charges generated by the element. The detector has an operative surface region in which variations with time in the intensity of radiation incident on every part of the region cause variations in the generated charges.    The volume of the element of pyroelectric material is less than would be the volume of an element of pyroelectric material which extended over the whole of the region and which had a thickness equal to the smallest spacing between the faces of the pair. Thermal diffusion devices extend to the element from parts of the operative surface region for supplying thermal energy to the element from radiation incident on said remote parts. The thermal capacitance of the thermal diffusion is less than the thermal capacitance of the element.    ADVANTAGE -   Has reduced Noise Equivalent Power (NEP). (7pp)    (GB2100058-B)      A pyroelectric detector comprising an element of pyroelectric material having at least one pair of opposed faces for generating electrical charges at the two faces of said one pair when the temperature of the element changes, and electrode means extending over at least one of the faces of said one pair for detecting charges generated by the element, the detector having an operative surface region on which the detector is adapted for radiation, whose intensity variations with time are to be detected, to be incident and variations with time in the intensity of radiation incident on every part of which region cause variations in the generated charges detectable with the electrode means, characterised in that the volume of the element of pyroelectric material is substantially less than would be the volume of an element of pyroelectric material which extended over the whole of said region and which has a thickness equal to the smallest spacing between the faces of said at least one pair, in that the detector comprises thermal diffusion means extending to the element from parts of said region remote therefrom for supplying thermal energy to the element from radiation incident on said remote parts, and in that the thermal capacitance of the thermal diffusion means is substantially less than the thermal capacitance of the element.t    (DE3220497-C)      The pyroelectric element described has an element of pyroelectric material that possesses at least a pair of opposite faces (2,3) of plastic film, on which electric charges are produced when the temp. of the element (1) changes, and electrodes (4,5) for detecting these charges which spread over at least one of these faces. There is an absorption surface (9) which can cause a temporary fluctuation of the intensity falling on it due to selective absorption, resulting in a fluctuation of the charges produced.    The volume of the element is essentially smaller than that required to cover the whole of the surface and it has a thickness equal to the smallest distance between the opposite faces mentioned. There is a heat dispersing arrangement (10) which lies between this surface and the element and which supplies the element with heat energy produced by the radiation falling on the area of the surface not over the element.    ADVANTAGE -   The advantage is a detector with an improved noise equivalent power.