PURPOSE: To reduce the number of lenses to lessen the variance of aberrations, by constituting a lens system with six lenses divided into the front group having a negative refracting power and the rear group having a positive refracting power and providing one aspherical face in the front group and satisfying specific conditions.

CONSTITUTION: The lens system is constituted with six lenses divided into the front group I having a negative refracting power and the rear group II having a positive refracting power, and one aspherical face is provided in the front group I at least, and the shortest focal length of the whole of the system is made shorter than the diagonal length of an effective screen. When the length from the object-side face to the image-side face of a lens I-1, the radius of curvature of a lens I-2, and the shortest focal length of the whole of the system are denoted as l, r3, and fs respectively, conditions of inequalities 1 and 2 are satisfied. The overall length of lenses is kept short by the inequality 1, and the variance of aberrations is reduced by the inequality 2, and the luminous flux toward the peripheral part of the screen is compensated in a wide angle region by the effect of the aspherical face. Thus, the number of lenses is reduced to make the lens system compact, and the variance of aberrations is lessened.