1974 年 43 巻 12 号 p. 1198-1204
Functions of optical lenses have changed with development of lasers and it becomes necessary to know their focal lengths more accurately.
In an optical system of hologram memory, for example, it is necessary to know the focal length with more than a 4th-order precision which is hardly possible with any of the conventional methods. This paper presents a new method for measuring focal lengths by using the telecentric system and by measuring the inclination of an incident narrow beam, and the distance between a deflected beam and the optical axis. It has several features; (1) simple in principle (2) the use of a laser beam (3) no need to observe images.
Application of this method to a ƒ=300 mm lens is discussed and it is verified theoretically and experimentally that measurement up to about a 5th-order precision is possible.