Ricoh (Pentax) filed a patent for a DSLR cameras focusing screen
Ricoh (Pentax) filed a patent for a DSLR cameras focusing screen (JP 2018-151549):
PROBLEM TO BE SOLVED: To provide a diffusing plate easy to see a subject image (real image) and a single lens reflex camera using the diffusing plate for a focusing screen.
SOLUTION: In order to observe a real image through an eyepiece optical system, a diffusing plate for forming the real image is planarly filled with at least two kinds of fixed microlenses having different peripheral shapes in a plan view as a repeating unit And a ring-shaped zone formed on the opposite side of the light diffusing face, wherein the planar filling mode of the microlens is non-periodic filling.
Via Hi-lows-note