Viewfinder optical system

An eyepiece lens consisting of a single lens element having a positive optical power, said single lens element having a refractive power of an aspherical surface and having a diffractive power,

• wherein the following condition is fulfilled:
• -0.0006<{1/(fl.multidot..nu.)}+.phi.DOE/.nu.DOE<0 0002
• where
• fl represents a focal length resulting from both refractive effect and diffractive effect of the eyepiece lens,
• .nu. represents an Abbe number of the eyepiece lens,
• .phi.DOE represents a power resulting from the diffractive effect of the eyepiece lens, and
• .nu.DOE represents an Abbe-number-equivalent value resulting from the diffractive effect of the eyepiece lens;
• wherein the eyepiece lens is formed in a meniscus shape.

An eyepiece lens consisting of a single lens element having a positive optical power, said single lens element having a refractive power of an aspherical surface and having a diffractive power,

• wherein the following condition is fulfilled:
• -0.0006<{1/(fl.multidot..nu.)}+.phi.DOE/.nu.DOE<0.0002
• where
• fl represents a focal length resulting from both refractive effect and diffractive effect of the eyepiece lens,
• .nu. represents an Abbe number of the eyepiece lens,
• .phi.DOE represents a power resulting from the diffractive effect of the eyepiece lens, and
• .nu.DOE represents an Abbe-number-equivalent value resulting from the diffractive effect of the eyepiece lens;
• wherein two surfaces of the eyepiece lens each have a diffractive power.

An eyepiece lens consisting of a single lens element having a positive optical power, said single lens element having a refractive power of an aspherical surface and having a diffractive power;

• wherein chromatic aberration resulting from the refractive power of an aspherical surface is substantially canceled by chromatic aberration resulting from the diffractive power;
• and
• wherein the following condition is fulfilled:
• -0.0006<{1/(fl.multidot..nu.)}+.phi.DOE/.nu.DOE<0.0002
• where
• fl represents a focal length resulting from both refractive effect and diffractive effect of the eyepiece lens,
• .nu. represents an Abbe number of the eyepiece lens,
• .phi.DOE represents a power resulting from the diffractive effect of the eyepiece lens, and
• .nu.DOE represents an Abbe-number-equivalent value resulting from the diffractive effect of the eyepiece lens.

A real-type viewfinder optical system comprising:

• an eyepiece lens system;
• and
• an objective lens system;
• wherein one of said eyepiece lens system and said objective lens system includes a lens element which has a surface having a diffractive power,
• wherein the following condition is fulfilled:
• 0.01<.vertline..phi.DOE/.phi.e.vertline.<0.16
• where
• .phi.DOE represents a composite power of the surface having a refractive power and a surface having a diffractive power within the lens element, and
• .phi.e represents a composite power of surfaces having refractive powers and surfaces having diffractive powers within said one of said eyepiece lens system and said objective lens system having said lens element therein.

A real-type viewfinder optical system comprising an eyepiece lens system having a lens element which has a surface having a diffractive power,

• wherein the following condition is fulfilled:
• 0.01<.vertline..phi.DOE/.phi.e.vertline.<0.16
• where
• .phi.DOE represents a composite power of the surface having a refractive power and a surface having a diffractive power within the lens element, and
• .phi.e represents a composite power of surfaces having refractive powers and surfaces having diffractive powers within the entire eyepiece lens system;
• wherein the surface having a diffractive power within the lens element constitutes part of an outer covering of an optical apparatus.

A real-type viewfinder optical system comprising:

• an objective lens;
• an objective-side inverting prism;
• and
• an eyepiece-side inverting prism;
• wherein:
• said eyepiece-side inverting prism has a diffractive optical surface formed on a pupil side surface,
• said pupil side surface of said eyepiece-side inverting prism has a curved surface, and wherein the following condition is fulfilled:
• 0.03<rE.multidot..phi.D/(1--N)<0.1
• where
• rE represents the radius of curvature of the pupil side surface of the inverting prism,
• .phi.D represents the power of the diffractive optical surface DOE provided on the pupil side surface of the inverting prism, and
• N represents the refractive index of the inverting prism.