| 摘要 |
PURPOSE:To provide the simple diaphragm device of good stability by performing exposure adjustment through insertion of an aperture blade from near the positions where luminous fluxes intersect and further compensating so-called cos<4> law approximately in a certain region. CONSTITUTION:An aperture blade 22 is mounted about the revolving shaft 28 installed near the position where luminous fluxes intersect and is so constituted as to perform exposure adjustment by rotating a winding shaft 23 by a diaphragm- pulling-out wire 26. The shape in the slit lengthwise direction of the aperture blade 22 is formed to that of quadratic curve form such as the one by which the vignetting amount of lens is gradually decreased as it goes toward the peripheral part. The adoption of such constitution permits not only the symmetrically stopping down of the luminous fluxes approximately and symmetrically from both ends but also the compensation of so-called cos<4> law. |
