| 摘要 |
PURPOSE:To obtain a high-performance, low-cost lens by allowing an optical system which consists of a negative and a positive lens from an entrance pupil side to meet specific requirements. CONSTITUTION:The optical system consists of the 1st negative lens and the 2nd positive lens successively from the entrance pupil side. This optical system satisfies inequalities I -IV, where n1 and n2 are the refractive indexes of the lenses, r1, r2, r3, and r4 are the radii of curvature of respective refracting surfaces, and (f) is the composite focal length of the whole system. Consequently, two- element constitution having a wide angle of view is realized, inexpensive plastic is usable as glass material, and various aberrations are compensated excellently. |
