PROJECTION LENS

PURPOSE:To realize a high focus by constituting the title lens of four groups containing a meniscus lens whose both faces are both convex faces against a screen, a biconvex positive lens, a lens which has a biconvex center part and weak positive refracting power, and a negative lens having a concave face on the screen side, and allowing the respective lens groups to satisfy the specific conditions. CONSTITUTION:The title lens is constituted of a first group containing a meniscus lens whose both faces are both convex faces against a screen, a second group containing a biconvex positive lens, a third group containing a lens which has a biconvex center part and weak positive refracting power, and the fourth group containing a negative lens having a concave face on the screen side in order from the screen side, and allowed to satisfy the conditions of the expression I. In the expression I, f0 and f1-f4 denote a focal distance of the whole lens system, and focal distances of the first-the fourth groups, respectively. In such a way, the contrast of a projected image is improved remarkably, and also, an optical system whose focus performance in the center part and the peripheral part of the screen is excellent can be realized.