| 摘要 |
Provided are an ocular zoom optical system which has a wide apparent field of view even on a low power side and in which aberrations are favorably corrected while a sufficient eye relief is secured over the entire zoom range, and an optical instrument including the ocular zoom optical system. The ocular zoom optical system 3 includes, in order from the object side: a first lens group G1 having a negative refractive power; a second lens group G2 having a positive refractive power; and a third lens group G3 having a positive refractive power and at least one aspheric surface. An intermediate image I' is formed between the first lens group G1 and the second lens group G2. During zooming, the third lens group G3 is fixed on the optical axis, and the first lens group G1 and the second lens group G2 are moved in directions opposite to each other with the intermediate image I' interposed therebetween. The second lens group G2 includes, in order from the object side: a positive single lens L21 having a higher positive refractive power on the lens surface on the eye-point side than that on the lens surface on the object side; and a positive cemented lens CL2 including a positive lens L22 and a negative lens L23. |
