344-359) describes a micrometer in which a negative lens is introduced between the eye-piece and the objectglass.

双重图象测微表与分开的透镜。各种各样的测微表被发明了除heliometer 以外为测量由重象。Ramsdens 屈光的测微表包括一个分开的透镜被安置在一台地球望远镜的架设的眼睛管的最内在的透镜的共轭焦点。