Zoom lens
AssigneeCanon Kabushiki Kaisha
InventorYoshinori Itoh
Life of this patent
Estimating the term…
Abstract
A zoom lens comprising, from front to rear, a first lens unit of positive refractive power and a second lens unit of negative refractive power, zooming being performed by varying a separation between the first lens unit and the second lens unit, wherein the first lens unit has at least two positive lenses and at least two negative lenses, and wherein the distance for the telephoto end from the first lens surface to the last lens surface, the diagonal length of the effective area of an image frame, the shortest and longest focal lengths of the entire system are appropriately determined.
Claims31
A zoom lens comprising, from front to rear, a first lens unit of positive refractive power and a second lens unit of negative refractive power, zooming being performed by varying a separation between said first lens unit and said second lens unit, wherein said first lens unit has at least two positive lenses and at least two negative lenses, wherein said first lens unit has a diaphragm at a position most close to an image plane side, and wherein, letting the distance from the first lens surface to the last lens surface in a telephoto end be denoted by DLT, the diagonal length of the effective area of an image frame by LY and the shortest and longest focal lengths of the entire system by fW and fT, respectively, the following conditions are satisfied:
- 0.22<DLT/fT<0.43
- 1.31<LY/fW<1.88.
A zoom lens comprising, from front to rear, a first lens unit of positive refractive power and a second lens unit of negative refractive power, zooming being performed by varying a separation between said first lens unit and said second lens unit, wherein said first lens unit has at least two positive lenses and at least two negative lenses, and the frontmost one of the negative lenses in said first lens unit has an aspheric surface of such shape that a negative refractive power gets progressively stronger as going from the lens center to the margin, and wherein, letting a refractive index of the material of the frontmost one of the negative lenses be denoted by NaL, the following condition is satisfied:
- 1.65<NaL,
- and
- wherein the aspheric surface of the frontmost one of the negative lenses in said first lens unit is a lens surface on an image side, and a lens surface on an object side of the frontmost negative lens has a radius of curvature RaF made to satisfy the following condition:
- -0.37<RaF/fT<-0.11
- where fT is the longest focal length of the entire system.
A zoom lens comprising, from front to rear, a first lens unit of positive refractive power and a second lens unit of negative refractive power, zooming being performed by varying a separation between said first lens unit and said second lens unit, wherein said first lens unit has at least two positive lenses and at least two negative lenses, and wherein, letting the distance from the first lens surface to the last lens surface in a telephoto end be denoted by DLT, the diagonal length of the effective area of an image frame by LY and the shortest and longest focal lengths of the entire system by fW and fT, respectively, the following conditions are satisfied:
- 0.22<DLT/fT<0.43
- 1.31<LY/fW<1.88,
- wherein said first lens unit includes at least four lens elements, and adjacent lens elements thereof have a different curvature on their opposing surfaces.
A zoom lens comprising, from front to rear, a first lens unit of positive refractive power and a second lens unit of negative refractive power, zooming being performed by varying a separation between said first lens unit and said second lens unit, wherein said first lens unit has at least two positive lenses and at least two negative lenses, and wherein, letting the distance from the first lens surface to the last lens surface in a telephoto end be denoted by DLT, the diagonal length of the effective area of an image frame by LY and the shortest and longest focal lengths of the entire system by fW and fT, respectively, the following conditions are satisfied:
- 0.22<DLT/fT<0.43
- 1.31<LY/fW<1.88,
- wherein said first lens unit includes at least four lens elements separated by air spacing.
A zoom lens comprising, from front to rear, a first lens unit of positive refractive power and a second lens unit of negative refractive power, zooming being performed by varying a separation between said first lens unit and said second lens unit, wherein said first lens unit has at least two positive lenses and at least two negative lenses, wherein said first lens unit has a diaphragm at a position most close to an image plane side, and wherein, letting the distance from the first lens surface to the last lens surface in a telephoto end be denoted by DLT, the diagonal length of the effective area of an image frame by LY and the shortest and longest focal lengths of the entire system by fW and fT, respectively, the following conditions are satisfied:
- 0.22<DLT/fT<0.43
- 1.31<LY/fW<1.88,
- wherein said first lens unit has at least one cemented lens.
A zoom lens comprising, from front to rear, a first lens unit of positive refractive power and a second lens unit of negative refractive power, zooming being performed by varying a separation between said first lens unit and said second lens unit, wherein said first lens unit has at least two positive lenses and at least two negative lenses, wherein said first lens unit has a diaphragm at a position most close to an image plane side, and wherein, letting the distance from the first lens surface to the last lens surface in a telephoto end be denoted by DLT, the diagonal length of the effective area of an image frame by LY and the shortest and longest focal lengths of the entire system by fW and fT, respectively, the following conditions are satisfied:
- 0.22<DLT/fT<0.43
- 1.31<LY/fW<1.88,
- wherein the lens of said first lens unit closest to the object side of said first lens unit is a positive lens.
A zoom lens comprising, from front to rear, a first lens unit of positive refractive power and a second lens unit of negative refractive power, zooming being performed by varying a separation between said first lens unit and said second lens unit, wherein said first lens unit has at least two positive lenses and at least two negative lenses, and wherein, letting the distance from the first lens surface to the last lens surface in a telephoto end be denoted by DLT, the diagonal length of the effective area of an image frame by LY and the shortest and longest focal lengths of the entire system by fW and fT, respectively, the following conditions are satisfied:
- 0.22<DLT/fT<0.43
- 1.31<LY/fW<1.88,
- wherein said first lens unit includes at least four lens elements, and adjacent lens elements thereof have a different curvature on their opposing surfaces, and
- wherein the lens of said first lens unit closest to the object side of said first lens unit is a positive lens.
A zoom lens comprising, from front to rear, a first lens unit of positive refractive power and a second lens unit of negative refractive power, zooming being performed by varying a separation between said first lens unit and said second lens unit, wherein said first lens unit has at least two positive lenses and at least two negative lenses, and wherein, letting the distance from the first lens surface to the last lens surface in a telephoto end be denoted by DLT, the diagonal length of the effective area of an image frame by LY and the shortest and longest focal lengths of the entire system by fW and fT, respectively, the following conditions are satisfied:
- 0.22<DLT/fT<0.43
- 1.31<LY/fW<1.88,
- wherein said first lens unit includes at least four lens elements separated by air spacing, and
- wherein the lens of-said first lens unit closest to the object side of said first lens unit is a positive lens.
Dependencies are inferred from the claim text.