When viewing extended objects, the apparent brightness seen in the eyepiece is a function only of aperture and magnification, it is not related to focal ratio.
当观察扩展光源时，目镜中所看到的亮度只跟孔径和放大率有关，它跟焦比并没有关系。
2
As a functional material or filling are need higher content brightness narrowly particle size distribution and radius-thickness ratio.
云母作为功能材料或填料都需要高纯度、细的粒度和窄的粒度分布、高白度和高径厚比。
3
Its advantages are discarding thick and heavy cover glass, high utilization ratio of energy, high brightness of refraction image, easy to making plane frame of hologram for display and easy to carry.