Compact zoom lens for video camera

Abstract

Abstract PURPOSE:To obtain a lightweight, compact lens by specifying the resultant refracting force of a 3rd group, a 4th group, and the rear group of a 5th group and the relation of the on-axis gap between a 2nd and the 3rd group in a telephoto end infinite-distance state. CONSTITUTION:The 1st group I is a fixed positive lens group, the 2nd group II is a negative lens group which moves for power variation at the time of zooming, and the 3rd group III is a negative lens group which is used even for focusing while an image plane is made constant at the time of zooming; and the 4th group IV is a fixed positive lens group composed of one positive lens IV-1 which makes divergent luminous flux from the 3rd group III sort of convergent and the 5th group V consists of the front group VA and rear group V5B. The front group consists of a positive lens VA-1 having a high-refractive-indexd surface on an object side and a negative lens VA-2 having a high-refractive-index surface on the object side, and the rear group is a three-element positive lens group consisting of a positive lens VB-1, a negative meniscus lens VB-2 having a convex surface on the object side, and a positive lens VB-3 having a large-refractive-index surface on the object side. Then, there is a stop between the 4th group IV and the 5th group V and meets requirements shown by inequalities I.

Inventors

• 👤 Masami Tanaka
• 👤 政美 田中

Bibliographic Details