Because maximum field of view in telecentric systems directly relates to the lens aperture closest to the object, larger front lenses are necessary for larger fields of view.
由于在远心系统中最大视场直接关系到镜头的镜头的光圈到物体之间的距离，若需要大的视场就必须要有大尺寸的前置镜头。
Refraction - Using an instrument called a phoropter, your optometrist places a series of lenses in front of your eyes and measures how they focus light.
屈光状态检测——通过使用综合屈光检测仪，验光师将一套镜片放在眼镜的前面测量出眼球是如何聚焦光线的。
Owing to the PTD effect in the lenses of spatial filter, large temporal front distortion of femtosecond pulses occurs in the spatial filter.
由于透镜传输时间延迟效应（PTD），飞秒激光脉冲经过空间滤波器产生脉冲波前变形。
Long telephoto lenses with many elements are probably more difficult to use. External filters in front of the lens can also increase flare.
组件繁多的长焦镜头也许会更难驾驭，镜头前端如果使用了外置滤镜也会助长眩光。
Using an instrument called a phoropter, an optometrist places a series of lenses in front of your eyes and measures how they focus light using a hand held lighted instrument called a retinoscope.
在使用综合验光仪时，验光师会将一套的镜片放在眼睛的前面，并通过一种名叫眼底镜的轻便简易的仪器测量出它们是如何聚焦光线的。
Using an instrument called a phoropter, an optometrist places a series of lenses in front of your eyes and measures how they focus light using a hand held lighted instrument called a retinoscope.
在使用综合验光仪时，验光师会将一套的镜片放在眼睛的前面，并通过一种名叫眼底镜的轻便简易的仪器测量出它们是如何聚焦光线的。
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