Zoom lens
AssigneeCanon Kabushiki Kaisha
InventorsKouji Hoshi, Takeshi Koyama, Yoshinori Itoh, Makoto Misaka, Akihiro Nishio
Life of this patent
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Abstract
A zoom lens is disclosed comprising, from front to rear, a first lens unit having a positive refractive power, a second lens unit having a positive or negative refractive power, a third lens unit having a positive refractive power, and a fourth lens unit having a negative refractive power, wherein rules of design are set forth in order to minimize the bulk and size of the lens system.
Claims35
A zoom lens comprising, from front to rear, a first lens unit of positive refractive power, a second lens unit, a third lens unit of positive refractive power, and a fourth lens unit of negative refractive power, separations between said lens units being varied to effect zooming,
- wherein said zoom lens satisfies the following condition:
- M.sub.1 =M.sub.2 =1,
- where Mi is the number of lens elements in said i-th lens unit, wherein, for a cemented lens, its constituent elements are counted as if in broken contact, and
- wherein said first lens unit moves at the time of zooming.
A compact zoom lens comprising, from front to rear, a first lens unit including at least one positive lens and having a positive refractive power as a whole, a second lens unit including at least one negative lens and having a negative refractive power as a whole, a third lens unit including at least one positive lens and at least one negative lens, and a fourth lens unit including at least one positive lens and at least one negative lens, separations between said lens units being varied to effect zooming, and said zoom lens satisfying the following conditions:
- 0.49<f.sub.3 /(f.sub.W .multidot.tan .omega..sub.W)<3.05
- 0.49<.vertline.f.sub.4 .vertline./(f.sub.W .multidot.tan .omega..sub.W)<3.0 5
- 0<d.sub.2W /(f.sub.W .multidot.tan .omega..sub.W)<0.55
- -1.21<(d.sub.2T -d.sub.2W)/(d.sub.3T -d.sub.3W)<0.21
- 0.11<B.sub.3 /f.sub.W <0.61
- where
- f.sub.3 and f.sub.4 :
- the focal lengths of said third lens unit and said fourth lens unit, respectively;
- f.sub.W and f.sub.T :
- the shortest and longest focal lengths of the entire system, respectively;
- .omega..sub.W :
- the semi-angle of field coverage of the entire system in a wide-angle end;
- d.sub.2W and d.sub.2T :
- the separations between said second lens unit and said third lens unit in the wide-angle end and in a telephoto end, respectively;
- d.sub.3W and d.sub.3T :
- the separations between said third lens unit and said fourth lens unit in the wide-angle end and in the telephoto end, respectively;
- and
- B.sub.3 :
- the axial length of said third lens unit.
A compact zoom lens comprising, from front to rear, a first lens unit of positive refractive power, a second lens unit of positive refractive power, a third lens unit of positive refractive power and a fourth lens unit of negative refractive power, separations between said lens units being varied to effect zooming, wherein said first lens unit includes at least one positive lens having a convex surface facing the object side, said second lens unit is constructed with a single lens satisfying the following condition, said third lens unit includes at least one negative lens and a positive lens having a convex surface facing the image side, and said fourth lens unit includes at least one positive lens having a convex surface facing the image side and a negative lens having a concave surface facing the object side, said condition being:
- -0.09<(R.sub.2F +R.sub.2R)/(R.sub.2F -R.sub.2R).multidot.(f.sub.W /f.sub.2)<2.51
- where
- R.sub.2F and R.sub.2R :
- the radii of curvature of the front and rear lens surfaces of said second lens unit, respectively;
- f.sub.W :
- the shortest focal length of the entire system;
- and
- f.sub.2 :
- the focal length of said second lens unit.
A compact zoom lens comprising, from front to rear, a first lens unit of positive refractive power, a second lens unit of positive refractive power, a third lens unit of positive refractive power and a fourth lens unit including at least one positive lens and one negative lens and having a negative refractive power as a whole, separations between said lens units being varied to effect zooming, and said zoom lens satisfying the following conditions:
- 1.17<(.phi..sub.1 +.phi..sub.2 +.phi..sub.3)/.phi..sub.W <2.22
- 1.17<.vertline..phi..sub.4 .vertline./.phi..sub.W <2.22
- 0.23<(B.sub.1 +B.sub.2 +B.sub.3)/(f.sub.W .multidot.tan .omega..sub.W)<1.50
- 0.11<SK.sub.W /TD.sub.W <0.31
- 1.21<(TD.sub.W +SK.sub.W)/(f.sub.W .multidot.tan .omega..sub.W)<3.31
- where
- .phi.i:
- the refractive power of the i-th lens unit;
- .phi..sub.W and f.sub.W :
- the overall refractive power and overall focal length of the entire lens system in a wide-angle end, respectively;
- Bi:
- the axial length of the i-th lens unit;
- .omega..sub.W :
- the semi-angle of field coverage of the entire lens system in the wide-angle end;
- and
- SK.sub.W and TD.sub.W :
- the back focal distance and physical length of the entire lens system in the wide-angle end.
A zoom lens comprising, from front to rear, a positive first lens unit, a positive second lens unit, a positive third lens unit and a negative fourth lens unit, air separations between said lens units being varied to effect zooming, wherein said first lens unit has a frontmost surface of concave curvature and said fourth lens unit includes a positive meniscus lens convex toward an image side followed toward the image side by a negative lens.
A zoom lens comprising, from front to rear, a positive first lens unit, a positive second lens unit, a positive third lens unit and a negative fourth lens unit, air separations between said lens units being varied to effect zooming, and said zoom lens satisfying the following condition:
- 0<D.sub.2 /f.sub.W <0.05
- where D.sub.2 is the distance from the first lens surface to the last lens surface of said second lens unit, and f.sub.W is the shortest focal length of the entire system.
A zoom lens comprising, from front to rear, a positive first lens unit, a positive second lens unit, a positive third lens unit and a negative fourth lens unit, air separations between said lens units being varied to effect zooming, wherein said third lens unit includes a negative lens having a concave surface facing an object side, a positive lens having a convex surface facing the object side, a negative lens and a bi-convex lens arranged in this order, and said fourth lens unit includes a positive meniscus lens convex toward an image side followed toward the image side by a negative lens.
A zoom lens comprising, from front to rear, a positive first lens unit, a positive second lens unit, a positive third lens unit and a negative fourth lens unit, wherein said first lens unit includes negative and positive lenses, said second lens unit has a stop movable in unison with said second lens unit, and said fourth lens unit includes a positive lens and a negative lens in this order.
A zoom lens comprising, from front to rear, a positive first lens unit, a positive second lens unit, a positive third lens unit and a negative fourth lens unit, air separations between said first lens unit and said second lens unit, between said second lens unit and said third lens unit, and between said third lens unit and said fourth lens unit being varied to effect zooming, wherein said second lens unit comprises a positive meniscus lens convex toward an image side, and said fourth lens unit comprises positive and negative lenses, totaling two lenses.
A zoom lens comprising, from front to rear, a positive first lens unit, a positive second lens unit, a positive third lens unit and a negative fourth lens unit, air separations between said lens units being varied to effect zooming, wherein said fourth lens unit includes a positive meniscus lens convex toward an image side followed toward the image side by a negative lens and satisfies the following condition:
- 0.5<ra/rb<1
- where ra is the radius of curvature of a rear surface of said positive meniscus lens, and rb is the radius of curvature of a front surface of said negative lens.
A zoom lens having a stop and comprising, from front to rear, a first lens unit of positive refractive power, a second lens unit of relatively weak refractive power, a third lens unit of positive refractive power and a fourth lens unit of negative refractive power, wherein during zooming from a wide-angle end to a telephoto ends, a separation between said first lens unit and said second lens unit increases, a separation between said second lens unit and said third lens unit varies and a separation between said third lens unit and said fourth lens unit decreases, wherein at least one lens included in said second lens unit lies on an image side of said stop, and wherein said second lens unit and said third lens unit are moved forward to effect focusing from an infinitely distant object to shorter object distances.
A compact zoom lens comprising, from front to rear, a first lens unit of positive refractive power, a second lens unit, a third lens unit of positive refractive power and a fourth lens unit of negative refractive power, said lens units being moved along an optical axis to effect zooming, a stop being arranged on an object side of said third lens unit, and focusing being performed by moving said third lens unit.
A zoom lens comprising, from front to rear, a first lens unit of positive refractive power, a second lens unit of positive refractive power, a third lens unit of positive refractive power and a fourth lens unit of negative refractive power, said first, said second, said third and said fourth lens units being moved along an optical axis in the same direction during zooming, and said zoom lens satisfying the following condition:
- 0<Bd/Fw<1.3
- where Bd is the entire length of said first lens unit, and FW is the shortest focal length of the entire system.
A zoom lens comprising, from front to rear, a first lens unit of positive refractive power, a second lens unit, a third lens unit of refractive power, and a fourth lens unit of negative refractive power, separations between said lens units being varied to effect zooming,
- wherein said zoom lens satisfies the following condition:
- 1.ltoreq.M.sub.2 <M.sub.1 .ltoreq.M.sub.4 <M.sub.3 .ltoreq.6
- where Mi is the number of lens elements in said i-th lens unit, and wherein, for a cemented lens, its constituent elements are counted as if in broken contact.
Dependencies are inferred from the claim text.