Reflex, magnifying optical system
A first lens group in a reflex, magnifying optical system includes sequentially from the side of an object, a first lens that has a negative refractive power and is a meniscus lens having a concave aspect facing toward an image, an optical element (prism) that refracts an optical path, a second lens having a negative refractive power and a concave aspect facing toward the object, and a third lens having a positive refractive power. A portion of an image-side aspect of the first lens abuts a plane of incidence of the optical element. A portion of an object-side aspect of the second lens abuts a plane of transmission of the optical element.
1. A reflex, magnifying optical system that is a variable-magnification optical system having a plurality of lens groups and varying magnification by moving any of the lens groups, the reflex, magnifying optical system comprising:
an optical element that is a prism refracting an optical path, an aspect of the prism on an object-side including straight edges symmetrical with respect to an optical axis;
a first lens that includes planes parallel with the optical axis and symmetrical with respect to the optical axis, and includes a concave aspect facing the object-side of the optical element, a perimeter of the planes abutting the straight edges of the aspect of the optical element, and
a second lens that includes a concave aspect facing an image side of the optical element with a radius of the second lens being smaller than a radius of the image side of the optical element and abuts the image side of the optical element.
2. The reflex, magnifying optical system according to claim 1 , wherein
the first lens has a negative refractive power and an aspheric surface on both sides,
and
the second lens includes two lenses abutting each other and has a negative refractive power.
3. The reflex, magnifying optical system according to claim 2 , comprising four lens groups,
wherein a first lens group consists of:
the first lens;
the optical element; and
the second lens,
a second lens group consists of three lenses and has a positive refractive power,
a third lens group consists of a single lens and has a negative refractive power, and
a fourth lens group consists of a single positive lens with a convex aspect facing toward an image.
4. The reflex, magnifying optical system according to claim 3 , wherein at least two lenses of the second lens group are cemented together.