| 摘要 |
PROBLEM TO BE SOLVED: To obtain a rigid mirror objective optical system which is lessened in image deterioration by a fluctuation in production by providing the optical system with a front group divergent system which includes a lens of negative power and is arranged in front of an incident pupil and a rear group convergent system which includes at least one distributed refractive index lenses and is arranged behind the incident pupil and satisfying specific conditions. SOLUTION: This optical system has, successively from an object side, the front group divergent system which includes the lens of a homogeneous medium having a concave face on an image side and having the negative power and is arranged in front of the incident pupil and the rear group convergent system which includes at least one distributed refractive index lenses and is arranged behind the incident pupil. The system is so constituted as to satisfy the conditions D>0.7Φand dG>Φ, where D denotes the length in terms of air between the face having the power on the extreme image side of the front group divergent system and the face having the power on the extreme object side of the rear group convergent system, dG denotes the sum of all the thicknesses of the distributed refractive index lenses,Φdenotes the outside diameter of the distributed refractive index lenses. The optical system which has a good assembly characteristic and is capable of dealing with a wide visual field angle is obtd. by constituting the optical system in such a manner.
|
