X-ray image intensifier and method for manufacturing thereof

An X-ray image intensifier, comprising a substrate of aluminum or aluminum alloy pressed to have a substantially spherical shape with a concave surface and an input screen having an X-ray excited phosphor layer which is formed of an aggregate of columnar crystals disposed on the concave surface and a photocathode disposed on the phosphor layer, wherein a ratio (L.ave/D) of an average length L.ave (unit:

• μm) between the neighboring bottoms of the gentle irregularities to a diameter D (unit:
• mm) of a region having the concave side of the substrate is in a range of 0.35 to 0.65;
• where the measurement determines an average length between the neighboring bottoms in the horizontal direction and an average height from peaks to bottoms from a profile of irregularities obtained by linearly measuring in a range of 2.0 mm to 4.0 mm in a given direction on the center region of the concave surface of the substrate;
• but minute irregularities which have a length of less than 20 μm between the neighboring bottoms in the horizontal direction and a height of less than 0.2 μm from peaks to bottoms and minute irregularities which have a length of 5 μm or below in the horizontal direction regardless of the height are excluded from the peaks or bottoms for measuring.

A method of manufacturing an X-ray image intensifier comprising:

• a pressing step for pressing an aluminum or aluminum alloy substrate material into a substantially spherical shape with a concave surface;
• a burnishing step for crushing minute projections of the concave surface of the pressed substrate;
• and
• an input screen forming step for depositing an X-ray excited phosphor layer formed of an aggregate of columnar crystals on to the concave surface of the substrate and depositing a photocathode on the phosphor layer.