F theta objective

The utility model relates to a F theta objective, this F theta objective include four simple lenses, have: as the biconcave lens have focus f1 first simple lens L1, as meniscus have focus f2 secondsimple lens L2, as plano -convex lens L3 have focus f3 third simple lens L3, as the fourth simple lens L4 who has a focus f4 of biconvex lens to and total focus f of this F theta objective, wherein these focuses f1 F4 and the relation that should assemble between the focus f satisfy following condition: 2.0&lt, F1f&lt, 1.8, 2.6&lt, F2f&lt, 2.0, + 1.1&lt, F3f&lt, + 1.6, 1.4&lt, F4f&lt, + 1.9. These objective have 355nm the wavelength and between 150mm and 190mm, especially for total focus of 170mm, this F theta objective can realize the formation of image of the reverse reflection of nothingof laser beam. 本实用新型涉及种F-θ物镜，该F-θ物镜包括四个单透镜，具有：作为双凹透镜的具有焦距f的第单透镜L、作为弯月形透镜的具有焦距f的第二单透镜L、作为平凸透镜L的具有焦距f的第三单透镜L、作为双凸透镜的具有焦距f的第四单透镜L，以及该F-θ物镜的总焦距f，其中这些焦距f-f与该总焦距f之间的关系满足以下条件：-2.0