PURPOSE: To provide a good balance between an image plane and spherical aberration in both of enlargement and reduction and to decrease the chromatic aberration and distortion aberration of the image plane by consisting a titled lens, successively when counted from a stop, of a specific convex meniscus lens, concave meniscus lens and convex meniscus lens.

CONSTITUTION: This lens consists, successively when counted from the stop, of the 1st lens which is the convex meniscus lens disposed by directing the concave face toward the stop, the 2nd lens which is the concave meniscus lens disposed by directing the concave face toward the stop and the 3rd lens which is the convex meniscus lens disposed by directing the concave face toward the stop. Said lens system satisfies the conditions expressed by the equations (1)W(5) and is disposed fully symmetrically with the stop. The equation (1) is the condition to determine the power of the 1st lens. The Petzval's sum is too small and the over curvature of field and the curved saggital image surface of astigmatism are resulted if the upper limit of the equation (2) is exceeded. The equation (3) relates to the correction of mainly the spherical aberration. The equation (4) controls the curving of the saggital image surface of the astigmatism and the equation (5) is for the correction of the chromatic aberration.