Patent ID: 9097887
Filing Date: 2015-08-04
Classification: G02B

Abstract:
1. A telescope optical system having an objective lens system and an eyepiece lens system; the telescope optical system being characterized in that: the objective lens system includes a first diffractive optical element, and a first cemented lens composed of a first lens having positive refractive power and a second lens having negative refractive power; the eyepiece lens system includes a second diffractive optical element, and a second cemented lens composed of a third lens having negative refractive power and a fourth lens having positive refractive power; the first diffractive optical element is composed of a first diffractive optical composing element having a first diffractive optical surface and a second diffractive optical composing element having a second diffractive optical surface, and the first diffractive optical composing element and the second diffractive optical composing element are arranged so that the first diffractive optical surface and the second diffractive optical surface face each other; the second diffractive optical element is composed of a third diffractive optical composing element having a third diffractive optical surface and a fourth diffractive optical composing element having a fourth diffractive optical surface, and the third diffractive optical composing element and the fourth diffractive optical composing element are arranged so that the third diffractive optical surface and the fourth diffractive optical surface face each other; and the condition represented by the following expression is satisfied: where: Ko represents the power of the objective lens system, Kodoe represents the power of the first diffractive optical element of the objective lens system, and Po is defined as Po=Kodoe/Ko; Ke represents the power of the eyepiece lens system, Kedoe represents the power of the second diffractive optical element of the eyepiece lens system, and Pe is defined as Pe=Kedoe/Ke; and FNO represents the F-number of the objective lens system, θ represents the real field of view of the telescope optical system, and m represents the magnification of the telescope optical system.