| 摘要 |
An optical system comprising, in the order from the object side, an objective lens unit having a positive refractive power, a relay lens unit having a positive refractive power and an eyepiece lens unit having a positive refractive power, adapted in such a manner that an inverted image formed by the objective lens unit is inverted once again by the relay lens unit for forming an erect image, using at least one graded refractive index lens element in the relay lens unit, and having a small number of lens elements or a high magnification and favorably corrected aberrations.
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