GB1523347A - Pyroelectric tragets - Google Patents

Abstract

1523347 Image pick-up tubes DEFENCE SECRETARY OF STATE FOR 16 Nov 1976 [17 Nov 1975] 47348/75 Headings H1K and H1D In a pyroelectric target, typically for a vidicon tube, comprising an array of pyro. electric elements 22, grooves (17), Fig. 3 (not shown) between the elements are filled with an epoxy resin having thermal diffusivity less than that of the pyroelectric elements so as to reduce lateral thermal diffusion in the target. The grooves (17) are formed either in a single crystal slice of lead germanate doped with silicon or boron, or in a pressed ceramic pyroelectric slice, either by photolithography followed by chemical etching, by using electron beam or by mechanical grinding. In one example, after filling the grooves with an epoxy resin, e.g. "Araldite" (Trade Mark) having thermal diffusivity less than 0À1 mm.<SP>2</SP> sec.<SP>-1</SP>, both the faces of the slice are polished so that the elements 22 are separated by a square network or epoxy resin regions 23. A front electrode 25, i.e. an electrode on which the thermal image is to be focused, of nickel/ chromium alloy comprises means 27 in contact with the elements 22, connected by narrow strips 29 of the electrode material so as to reduce lateral heat diffusion in the electrode. A back electrode structure having isolated elements may be provided on the surface of the target which is scanned by an electron beam in a vidicon tube. The lateral heat spread may further be reduced by grooving the epoxy resin regions. The ferroelectric domains of the target are aligned using a steady electric field. A pyroelectric vidicon tube employing the target, and an associated electrical circuit are described, Fig. 9 (not shown)