GB1299664A - Combined luminescent screen and anti-diffusion grid and method of making same - Google Patents

Abstract

1299664 Luminescent screens OPTISCHE INDUSTRIE "DE OUDE DELFT" NV 4 March 1970 [5 March 1969] 10400/70 Heading C4S [Also in Division H5] A combined X-ray luminescent and antidiffusion screen comprises a number of compartments containing luminescent material separated one from another by light reflecting walls the major surfaces of which extend parallel to the primary X-rays, the walls being formed of spaced apart strips of X-ray absorbent material, e.g. thin matallic strips 1, the compartments being filled with luminescent material 3 over a part of their height on the side remote from the X-ray source and for the remainder of their height, being transparent to X-rays (e.g. solid strips 2). Preferably the material of solid strips 2 is also light reflective, e.g. white. The screen inherently functions as an X-ray antidiffusion grid and the ratio of the remainder of the height to the spacing distance between adjacent strips (e.g. 0À3 to 1 mm.) is preferably greater than three. In a method of fabrication the grid of spaced strips may be placed one side in a layer of soluble material (e.g. paraffin wax and petroleum jelly mixture) of thickness equal to the luminescent layer to be formed, filling the remainder of the compartments with a selfhardening liquid (e.g. a thermosetting plastic such as an epoxy resin with a white pigment), removing the soluble material with a solvent such as petrol, and filling with luminescent material. A curved surface (18) spherical or cylindrical, may be used (Fig. 7, not shown) and the screen pressed to flatness before the selfhardening liquid solidifies to ensure direction of the strips to the X-ray focus. Fig. 8 (not shown). Protecting cover (23) and edge (20) may be provided. The screen may be circular (Fig. 2, not shown) spaced by corrugated or waved strip (5) with compartments (7), or flat (Fig. 3, not shown), the corrugated strips (16) of Fig. 4 (not shown) being filled with phosphor (13) over only a small portion of their height, and retained by p.v.a. layer (15), material (14) being highly X-ray transparent, a thin layer of same protecting the upper edges. In Fig. 5 (not shown), corrugated strips (16) are the full screen height, and in Fig. 6 (not shown), only the phosphor height, spaces (12<SP>1</SP>) being X-ray transparent. The walls of Fig. 2 may be focus aligned by pressing the outer strip during winding by a roller on a rod journalled at a point on the optical axis. The flat strips at least should have a high absorbtion for secondary X-rays, especially high A. Wt. metals of high specific absorbtion. 0À03 to 0À04 mm. Au and Ag are instanced. In Figs 4 and 5 for example, heavy flat strips and lighter waved strips may be used, and may be an alloy of light and heavy metals or a stratified combination of different materials. A medical X-ray image intensifier camera may include a 0À6 to 0À7 mm. thick phosphor layer. Reference is included to Specification 777,745.