F-NUMBER MEASURING DEVICE OF OPTICAL SYSTEM

摘要

PURPOSE: An F-number measuring device of an optical system is provided to measure the F number promptly with precision as well as to use a scale conveniently. CONSTITUTION: An F-number measuring device of an optical system consists of a base(10) having specific length(L) made of soft material, and front and rear plates(20,30) separated with specific length by the base and sequentially arranged in an incident direction of beam from a light system. The front plate is made of a transparent thin plate of glass or plastic while the rear plate is made of a screen for reflecting or transmitting beam. Concentric circles are drawn together with the central mark on the front and rear plates. The central mark of the rear plate is marked at a point with a normal of the front plate passing through the rear plate. Each concentric circle of the front and rear plates is marked in numerical value. The F number is measured immediately simply by setting the measuring device at a proper position without particular setting. Therefore, the measuring time is shortened.