| 摘要 |
PURPOSE:To increase the angle of view and ratio of diameters of a projection lens by using four groups of lenses and positioning the 2nd group lens at the entrance pupil position of the whole system. CONSTITUTION:The projection lens is so constituted that an over power chromatic aberration and an upper power chromatic aberration cancel each other by generating the over power chromatic aberration by the 4th group lens 4 and the under power chromatic aberration by the 3rd group lens 3. The 2nd group lens 2 which is a biconcave negative lens is arranged at or nearby the incidence position of the whole system. Consequently, the 2nd group lens 2 compensates an on-axis chromatic aberration without exerting any influence upon the power chromatic aberration.
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