Zoom lens device with four lens unit

A zoom lens device comprising in order of lens units, from object side to image side:

• a first lens unit having a positive refractive power, said first lens unit comprising a meniscus positive lens and a meniscus negative lens with their convex surfaces facing the object side;
• a second lens unit having a negative refractive power, said second lens unit comprising a meniscus negative lens having its convex surface facing the object side, a biconcave negative lens, and a meniscus positive lens having its convex surface facing the object side;
• a third lens unit having a positive refractive power, said third lens unit comprising one of (i) a biconvex positive lens and a negative lens and (ii) a meniscus negative lens with its convex surface facing the object side and a positive lens;
• and
• a fourth lens unit having either a positive or negative refractive power and comprising one of (i) a meniscus positive lens having its convex surface facing the image side and (ii) a biconvex positive lens and a biconcave negative lens,
• wherein said zoom lens device further comprises a stop disposed between said second lens unit and said fourth lens unit,
• wherein when magnification is being changed from a wide angle end to a telephoto end, said first lens unit, said third lens unit, and said fourth lens unit are moved toward the object side such that the distance between said first lens unit and said second lens unit increases, the distance between said second lens unit and said third lens unit decreases, and the distance between said third lens unit and said fourth lens unit changes,
• wherein the following conditions are satisfied:
• 1.5<f1/fw<4.5
• 0.4<-f2/fw<1.2
• where f1 is the focal length of said first lens unit, f2 is the focal length of said second lens unit, and fw is the focal length at the wide angle end of the entire lens system, and
• wherein at least one of the conditions (a) that said first lens unit has only two lenses, (b) that said second lens unit has only three lenses, (c) that said third lens unit has only two lenses, and (d) that said fourth lens unit has only one lens, is satisfied.

A zoom lens device comprising in order of lens units, from object side to image side:

• a first lens unit having a positive refractive power, said first lens unit comprising a meniscus negative lens and a meniscus positive lens having their convex surfaces facing the object side;
• a second lens unit having a negative refractive power, said second lens unit comprising a biconcave negative lens and a meniscus positive lens having its convex surface facing the object side;
• a third lens unit having a positive refractive power, said third lens unit comprising a biconvex positive lens and a meniscus negative lens with its convex surface facing the image side;
• and
• a fourth lens unit comprising a meniscus positive lens having its convex surface facing the image side,
• wherein said zoom lens device further comprises a stop disposed between said second lens unit and said fourth lens unit,
• wherein when magnification is being changed from a wide angle end to a telephoto end, said first lens unit, said third lens unit, and said fourth lens unit are moved toward the object side such that the distance between said first lens unit and said second lens unit increases, the distance between said second lens unit and said third lens unit decreases, and the distance between said third lens unit and said fourth lens unit changes,
• wherein the following conditions are satisfied:
• 1.5<f1/fw<4.5
• 0.4<-f2/fw<1.2
• where f1 is the focal length of said first lens unit, f2 is the focal length of said second lens unit, and fw is the focal length at the wide angle end of the entire lens system, and
• wherein at least one of the conditions (a) that said first lens unit has only two lenses, (b) that said second lens unit has only two lenses, (c) that said third lens unit has only two lenses, and (d) that said fourth lens unit has only one lens, is satisfied.

A zoom lens device comprising in order of lens units, from object side to image side:

• a first lens unit having a positive refractive power, said first lens unit comprising a positive lens and a meniscus negative lens with its convex surface facing the object side;
• a second lens unit having a negative refractive power, said second lens unit comprising a biconcave negative lens and a meniscus positive lens having its convex surface facing the object side;
• a third lens unit having a positive refractive power, said third lens unit comprising a biconvex positive lens and a meniscus negative lens with its convex surface facing the image side;
• and
• a fourth lens unit comprising a meniscus positive lens having its convex surface facing the image side,
• wherein said zoom lens device further comprises a stop disposed between said second lens unit and said fourth lens unit,
• wherein when magnification is being changed from a wide angle end to a telephoto end, said first lens unit, said third lens unit, and said fourth lens unit are moved toward the object side such that the distance between said first lens unit and said second lens unit increases, the distance between said second lens unit and said third lens unit decreases, and the distance between said third lens unit and said fourth lens unit changes,
• wherein the following conditions are satisfied:
• 1.5<f1/fw<4.5
• 0.4<-f2/fw<1.2
• where f1 is the focal length of said first lens unit, f2 is the focal length of said second lens unit, and fw is the focal length at the wide angle end of the entire lens system, and
• wherein at least one of the conditions (a) that said first lens unit has only two lenses, (b) that said second lens unit has only two lenses, (c) that said third lens unit has only two lenses, and (d) that said fourth lens unit has only one lens, is satisfied.