| 摘要 |
PURPOSE:To obtain an accurate pupil area independently of the variance of the light quantity level, by using light sources different in diameter and performing the measurement twice with different slice levels of a television signal to correct inclinations of luminance level curves mutually. CONSTITUTION:Pinholes P1 and P2 having radiuses r1 and r2 respectively are compatible with each other. The light from the pinhole placed in the focus position of a lens 1 to be measured projects the picture of a stop 2 of the lens 2 onto a screen 3. The projected pattern has the luminance level adjusted by an ND filter 4 and a transparent glass 6 and is projected onto the surface of a vidicon 9 by a taking lens 8. This projected pattern is swept by scanning lines to change the slice level for obtaining an electric signal. Pinholes are exchanged to obtain respective equivalent diameters of the pupil image for successive combinations of level change, and a true equivalent diameter of the pupil image is operated on a basis of the proportional relation between equivalent diameters of the pupil picture and obtained equivalent diameters, thus obtaining the F number of the lens. |
