An optical element including a first head lens array having at least first and second head lenses joined together by a bar, and at least one second bead lens array having at least a third head lenses arranged between the first and second head lenses.

In a method of making pixelated scintillators, an amorphous scintillator material in a molten state is pressed into a plurality of cavities defined by a plurality of walls of a mesh array. The molten scintillator material in the plurality of cavities is cooled to form a pixelated scintillator array. An x-ray imager including a pixelated scintillator is also described.

A mold apparatus of a lens array and a method for using the same are provided. The mold apparatus includes an upper pressing die, a lower pressing die and a plate structure. The upper pressing die includes a plurality of upper engaging portions. The lower pressing die includes a plurality of lower engaging portions. The plate structure includes a plurality of through holes. A glass article is installed at the through hole. The glass article includes a first sectional width W1. The through hole includes an upper opening and a lower opening. The upper opening corresponds to the upper pressing die. The lower opening corresponds to the lower pressing die. The upper opening includes a second sectional width W2. The lower opening includes a third sectional width W3. Wherein W1W2 or W1W3; the glass articles are extruded by the mold apparatus to manufacture the lens array.