PURPOSE: To realize stigmatization with a few number of sheets of lenses, by satisfying a various kinds of specific conditions with a lens system consisting of six groups.
CONSTITUTION: The titled system consists of six groups, a first lens group 1 having a negative refracting power for the incident direction of light, a second lens group 2 having a positive refracting power, a phase correction plate 3 as a third group having no refracting power, a phase correction plate 4 as a fourth group having no refracting power, a fifth lens group 5 having the positive refracting power and consisting of three sheets of positive lenses, and a sixth lens group 6 having the negative refracting power. Then, the conditions of equations IWIV are satisfied. In the equations IWIV, f1Wf6 represent the focal distances of the first group W the sixth group, and f456 represent the synthesized focal distances of the third group W the fifth group, and (f) represents the focal distance of the whole system. Thus, a negative power and a positive power are balanced almost equally, and the phase correction plate with few of power is arranged in the center. In such a way, it is possible to realize the stigmatization with a few number of sheets of the lenses.