JPH0625824B

• Main Authors: OOIZUMI KOJI, NAKAYAMA HIROKI, YAMADA YASUYUKI, SATO YASUHISA
• Format: Patent
• Language: English
• Published: 06.04.1994
• Edition: 5
• Subjects: OPTICAL ELEMENTS, SYSTEMS, OR APPARATUS; OPTICS; PHYSICS

PURPOSE:To compensate aberration efficiently over the whole screen by constituting the 2nd lens group of the 2-1th lens having concave surfaces on both the sides and the 2-2th meniscus-like lens turning its convex surface to the image side and having negative refractive force which are arranged successively from the object side. CONSTITUTION:The 2nd lens group is constituted of two negative lenses, i.e. the negative lens having concave surface on both the sides and the negative meniscus lens turning its concave surface to the object side which are arranged successively from the object side. Since the negative meniscus lens is improved in refractive force without increasing the curve of the image surface and the 1st lens of the 2nd lens group forms concave surfaces on its both sides, two negative lenses of the 2nd lens group take partial charge of negative refractive force each other and both the radiuses of curvature are moderate, so that the generation of a curve on the image surface is reduced at the generation of aberration. Consequently, a small zoom lens reducing the variation of the curve on the image surface due to variable power and efficiently compensating the aberration over the whole screen can be obtained.