PURPOSE: To obtain a bright triplet type lens with a wide angle of view by composing the lens of two lenses which have positive refracting power and are in specific relation and a lens which have negative refracting power.

CONSTITUTION: The lens system consists of a 1st lens with positive refracting power, a 2nd lens with negative refracting power, a 3rd lens with positive refracting power, and a stop; and at least one lens surface is aspherical and at least one term in an equation I satisfies an inequality II to obtain a bright triplet type with the wide angle of view. Here, Z is an aspherical surface shape, (c) the curvature of a peak point, K the constant of a circular cone, (p) the distance between a point on a lens surface and an optical axis, (k) the number of a term, nk the degree of the term, and ak the coefficient of the term.