单词focal length
n.: 【摄】焦距
焦距:
the distance between the centre of a mirror or a lens and its focus
〔物〕焦距
Spot diameters of just a few thousands of an inch can readily be attained with convenient short focal length lenses.
用普通的短焦距透镜不难得到直径只有几十微米的光点。
The focal length you need depends on your distance from the burst and what you"re trying to capture.
你所需要的焦距取决于你和被拍摄焰火间的距离，以及你想捕捉到怎样的画面。
Use angle encoder calibration coefficient of deviation of the long focal length of high-precision tracking system was satisfactory results.
利用编码器标定角偏差系数的方法，在长焦距高精度跟踪系统中获得了满意的效果。
Objective and the focal length of the specimen to be measured. The measurement of the size of the reticle.
十字线的像的尺寸取决于准直仪物镜的焦距和待测样品的焦距。
To determine power, divide the focal length of the telescope (in mm) by the focal length of the eyepiece (in mm).
将望远镜的焦距（单位：mm）除以目镜的焦距（单位：mm），就可以得到望远镜的放大率。
The focal length of the condensing lens should be such that the image of the source just fills the projecting lens.
聚光透镜的焦距应使光源的像正好照满放映透镜。
If you know the FOV, sensor size, and working distance, you can compute the focal length of the lens you need using the following formula.
如果你知道视野FOV，感应器大小，和工作距离，你能用以下之方程式去计算你所需之镜头的焦距。
It can be used to really evaluate the optical performance and imaging characters at any focal length of a zoom system.
可借助该程序对变焦系统任意焦距位置的光学性能和像差特性进行实时评估。
Using a longer focal length and photographing stars far from the north star increase the distance stars will move across the image.
使用长焦镜头拍摄远离北极星的星星，会增加星星在相片上移动轨迹。
Or, you can calculate the exit pupil by dividing the focal length of the eyepiece (in mm) by the focal ratio of the telescope.
或者，你还可以将目镜的焦距除以望远镜的焦比来得到出瞳尺寸。