Patent ID: 7952800

Claim:
A variable power relay optical system that forms a secondary image based on light from a primary image, comprising: a variable power lens system that carries out zooming the secondary image based on the light from the primary image; and a rear lens group that forms the secondary image based on the light passing through the variable power lens system; the variable power lens system consisting of, in order from the primary image side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a fourth lens group having positive refractive power, upon zooming from a high magnification end state to a low magnification end state, the fourth lens group being moved to the secondary image side, and a distance between the first lens group and the second lens group increasing, upon zooming the variable power lens system, positions of the primary image and the secondary image, an entrance pupil of the variable power relay optical system, a pupil of the variable power lens system, an exit pupil of the variable power relay optical system being substantially kept constant, and the pupil of the variable power lens system being disposed to the secondary image side of the last surface of the variable power lens system.