A refractive defect of a lens or other optical system that prevents light rays from converging at a single point resulting in a blurred or imperfect image.
散光有折射缺陷的透镜或其它光学系统，阻碍光线汇聚于一个焦点，形成一个模糊或不完全的图象。
2
That oval shape prevents light from converging on the retina.
这种椭圆形防止光线在视网膜上的趋同。
3
At least one aspherical lens is arranged between the spherical lens and the printing form, for focusing or converging the laser light onto a desired spot.