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
So far people have put forward some basic methods for evaluate the MTF values of the lens, such as knife-edge method, laser speckle method and extended frequency aperture (EFA) method.
迄今为止，人们已经提出了诸如刃边法、激光散斑法、扩展频率孔径法等多种测量离散成像器件MTF的方法。
3
The visual field of the reconstructed image is extended and is not limited by the aperture of the lens.