| 摘要 |
A high-aperture objective comprising a first lens L1 with positive refractive power f1 and a second lens L2 with negative refractive power f2, wherein the focal length ratio between the two lenses is in the range of -0.4<(f1/f2)<-0.1 and the total refractive power 1/f1+1/f2 is greater than zero, two positive lenses L3, L4 whose ratio diameter d3, d4 to focal length f3, f4 satisfies the condition greater than 0.3 and less than 0.6:0.3<d3/f3<0.6, 0.3<d4/f4<0.6, a negative lens L5 and a collective lens L6, wherein the negative lens faces the front group and the focal length ratio of L5 and L6 f5/f6 is between -0.5 and -2:-0.5<f5/f6<-2.
|
