A novel VFL (variable focal length) system of a long working length(117mm), a short focus and a continuous zoom type range from 18mm to 57mm is studied.
研究了一种长工作距离（117mm）、短焦距、在18～57mm范围内连续可变焦距的YAG激光加工机新型光学聚焦系统，论述了系统的特点及基本原理，给出了有关设计参数。
manual zoom lens
(镜头)手控可变焦距透镜
One of Visible Video Zoom System Research;
一种可见光变焦距电视光学系统研究
variable focal length (cylindrical) lens
变焦(距)(圆柱)透镜
autofocus zoom lens
自动聚焦变焦距镜头
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快速变焦距手术显微镜
rear-controlled zoom lens
背面调整变焦距透镜
best image plane of zoom lens
变焦距物镜的最佳像面
image plane displacement of zoom lens
变焦距物镜像面位移
auto iris zoom lens
自动光圈变焦距镜头
zoom stereomicroscope
快速变焦距立体显微镜
Performance Analysis of the Elliptic Beam Ring-focus Antenna with a Variable Focal Distance
椭圆波束变焦距环焦天线的性能分析
The wearer of such glasses could change the focus by sliding a switch along one arm of the frame.
带这种眼镜的人通过调整一只眼镜腿上的滑动开关可以改变焦距。
macro teleconverter
增距式微距附加镜﹝使标准镜头变成微距而保留最近封焦距离﹞
variable interval schedule
可变时距程序可变时距程序
universal zoom operation microscope
通用型变焦距手术显微镜
The focal length differs with the thickness of the lens
焦距长底随透镜的厚度而变化。
Having three focal lengths.
三焦距的有三个焦距的
equivalent focal length
当量焦距，等效焦距