| 摘要 |
PURPOSE:To obtain an inexpensive aspheric lens with superior optical performance by reducing the difference between the refractive indexes of a lens blank consisting of a glass lens and a plastic layer joined with the surface of the lens blank. CONSTITUTION:In the aspheric lens obtained by joining the plastic layer 1 to the surface of the lens blank consisting of a glass lens and forming the surface of the plastic layer as an aspheric surface, the difference between the refractive index based upon the main wavelength of the glass and that based upon the main component of plastic is set up to DELTAnXa/P<=5X10<-5>. Provided that, (a) and P are the roughness of the surface shape of the lens blank and its pitch. Namely, when the surface shape index a/P of the lens blank is reduced so that an incident angle alpha is reduced, the difference DELTAtheta between the refractive angles is reduced, or when the difference DELTAn between the refractive indexes of the glass and plastic is reduced (the ratio n1/n2 of both the refractive indexes is reached to '1'), the difference DELTAtheta of the refractive angles is also reduce, so that the excellent optical performance can be obtained. |
