A dark green, round biconvex tablet with opaque coating.

深绿色，圆形不透明涂层双凸片。

This paper, in detail, introduced how to study the rule of image construction for biconvex lens by using the method of vision difference.

本文详细地介绍了如何运用视差现象研究凸透镜的成象规律。

The rule of adaxial image formation is studied, of the transmission light and reflected light through the two optical surfaces L_1 and L_2 of the biconvex lens.

研究了经双凸透镜两个光具面 L_1和 L_2的透射光线和反射光线的近轴成像规律，以此说明其像群的形成。

The optical aberration difference between the biconvex Fresenl lens and the plane-convex Fresenl lens was investigated by designing a large aperture Fresenl lens.

通过一个大尺寸菲涅尔透镜的设计，比较了曲面菲涅尔透镜和平面菲涅尔透镜在光学像差方面的差异。