| 摘要 |
Circular and annular lens zones are disclosed which, at a given lens area, exhibit a depth of focus of a lens of considerably smaller area. The large depth of focus is achieved by imparting the lens zones a refractive power profile. An assembly of such large depth of focus lens zones represents a lens of large diameter which lens, in polychromatic light, exhibits essentially the same depth of focus as the lens zones from which it is composed. |
