To provide a compact, high-performance, inexpensive and light-weight lens for a CCTV by constituting a lens system consisting of a first diaphragm, a lens and a second diaphragm so that at least one surface thereof is aspherical and a specified condition is satisfied.

The lens system is constituted by arranging the first diaphragm, the aspherical meniscus lens L obtained by making the convex surface thereof having strong curvature face to an image surface side and provided with positive power and the second diaphragm in turn. By adopting at least one aspherical surface, the various kinds of aberration are excellently corrected. Besides, a plastic lens can be effectively used. In addition to such a shape characteristic, the constitutional condition of 4>D1+D2+D3 is satisfied. Where, D1 shows a distance to the first surface of the lens L from the first diaphragm, D2 shows the thickness of the lens L and D3 shows a distance to the second diaphragm from the second surface of the lens L. Since the whole length and the outside diameter of the lens system can be shortened as a whole on this condition, the high-performance and compact lens for a CCTV is realized.