Lens for optical disk

Abstract

Abstract PURPOSE:To correct the chromatic aberration satisfactorily by a three-group three-piece constituting lens, by specializing the relation of the synthetic focal length of all systems, the curvature radius of the junction surface of the first and second lenses, the refraction factor of the first - third lenses and the Abbe's number. CONSTITUTION:The lens is a two-group three-piece constituting lens, and satisfies the conditions of formulas 1-6. Here, the symbol (f) is the synthetic focal length of all systems of the lens, r2 is the curvature radius of the junction surface of the first and second lenses, N1-N3 are the refraction factor of the first - third lenses, and nu1-nu3 are the Abbe's number of the first - third lenses. When ¦r2¦ is larger than the upper limit, the achromatic action by the first group is small, and when N1 is smaller than the lower limit, the negative spherical aberration quantity in the first lens comes to be too large, and when N2-N1 is larger than the upper limit, the influence to the spherical aberrasion in the r2 surface comes to be too large, and when nu1-nu2 is smaller than the lower limit, the action to the correction of the chromatic aberration at the first group is too small, and when N3 is smaller than the lower limit, the generat ing quantity of the spherical aberration in respective aberrations of the second group comes to be too large. The formula 6 makes suitable the correction of the chromatic aberration.

Inventors

• 👤 Takahiro Sugiyama
• 👤 孝浩 杉山

Bibliographic Details