OPTICAL IMAGE FORMING LENS SYSTEM

摘要

An image pick-up optical system is provided to reduce the volume, to secure high resolution, and to minimize the deterioration of optical characteristics like such as flare. An image pick-up optical system(10) having a photoelectric conversion image sensor(S) includes a first lens group(G1) having the positive refractive force; a second lens group(G2) having the negative refractive force; a third lens group(G3) having the positive or negative refractive force; a fourth lens group(G4) having the positive or negative refractive force; a lens positioned in the first lens group and provided with at least one aspherical surface(R1,R2); and a thin film filter(LP) for restricting a portion of the light, between the second and third lens groups or between the third and fourth lens groups.