Three lens arrangement - has front, central and rear lens of material of different dispersions set spacedly and having spherical and aspherical surfaces

摘要

The front lends (10) and rear lens (14) have positive refraction force, whilst the middle lens (12) has negative refraction force. The distance between the front and middle lenses is smaller than that between the middle lens and the rear. Each lens has at least one aspherical surface (16,20,26), and one spherical surface (18,22,28). The aspherical surfaces are simple cone section rotation surfaces. The cone section coefficient of the aspherical surface on the front lens is less than 0.01, on the middle lens is less than -5, and on the rear lens is less than -0.1. ADVANTAGE - A lens arrangement with higher resolution and as few as possible lenses and reduced structural length.