PURPOSE: To provide an optical system for copying machine having high contrast and the brightness of F8 and capable of reducing the cost by using the glass of a low unit price by comprising the system of plural lens groups composed of single lenses, respectively, and satisfying a specified condition.
CONSTITUTION: This system is composed of a first lens group composing of a single lens having a positive refractive power, a second lens group composed of a single lens having a negative refractive power and a third lens group composed of a single lens having a positive refractive power successively arranged from the object side. The respective conditions: 0.37f<f1<1.6f, -0.31f<f2<0.19f, 1.55<n1<1.65, 2.3<(ν1+ν3)/ν2<3.3 are satisfied, where, f: the composite focal distance of a whole system for (d) line, f1, f2: focal distances of the first lens group and the second lens group for (d) line, respectively, n1: the refractive index of the first lens group for (d) line and ν1-ν3: the Abbe numbers of the first to the third lens groups 1-3, respectively.
JP2711128 | [Title of Invention] Lens for Copier |
JPH10311946 | TRIPLET LENS |
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