| 摘要 |
PURPOSE:To constitute a bright lens by constituting a titled lens system of a positive focusing lens, a negative variator, a negative compensator and a relay lens system, limiting a type of the third lens group and the relay lens system, and giving a numerical limit of ten pieces. CONSTITUTION:A titled lens system consists of the first focusing lens group whose refractive power is positive, the second lens group used as a negative variator, the third lens group used as a positive compensator, and a relay lens system in order from an object side. The first lens group consists of a negative meniscus lens, a positive lens and a positive meniscus lens, the second lens group consists of a positive lens and a negative and positive doublet, the third lens group consists of a positive lens and a doublet of positive and negative meniscus lenses, and the relay lens system consists of positive and negative lenses and positive and negative meniscus lenses leaving a space between them. A telephoto zoom lens of F2.8, whose zoom ratio is about 2 is constituted by giving a numerical limit of 10 pieces to items of the lens. |
