Patent ID: 10859811

Abstract:
A relay optical system includes, in order from, an object side, a first cemented lens, a second cemented lens having a positive refractive power, a third cemented lens which is plane-symmetric to the second cemented lens, and a fourth cemented lens which is plane-symmetric to the first cemented lens, the first cemented lens includes a first lens having a positive refractive power and a second lens having a negative refractive power, the second cemented lens includes a third lens and a fourth lens, a shape of the first lens is a biconvex shape, a shape of the second lens is a biconcave shape, and the following conditional expression (1), in which f2 denotes a focal length of the second lens and fCL12 denotes a combined focal length of the first cemented lens and the second cemented lens, is satisfied: −0.4<f2/fCL12<−0.1  (1).