Zoom lens system

A zoom lens system comprising, from the object side to the image side:

• a first lens unit of a positive refractive power;
• a second lens unit of a negative refractive power, said second lens unit consisting of, from the object side to the image side, a negative lens element whose image side surface has a stronger refractive power than its object side surface, a biconcave lens element, and a positive high dispersion lens element whose object side surface has a stronger refractive power than its image side surface;
• and
• a third lens unit of a positive refractive power, said third lens unit consisting of at least three and at most five lens elements including at least one aspherical surface;
• and wherein high dispersion includes an Abbe number of approximately 30 or lower, and at least said second and third lens units shift on an optical axis of said zoom lens system during the zooming operation, and wherein all of said lens units include at least one high dispersion lens element having a refractive power opposite to that of the lens unit.

A zoom lens system comprising, from the object side to the image side:

• a first lens unit of a positive refractive power;
• a second lens unit of a negative refractive power;
• and
• a third lens unit of a positive refractive power, said third lens unit consisting of, from the object side to the image side, a positive lens element and a negative lens element and having at least one aspherical surface;
• and wherein at least said second and third lens units shift on an optical axis of said zoom lens system during the zooming operation, and wherein all of said lens units include at least one high dispersion lens element having a refractive power opposite to that of the lens unit with an Abbe number of approximately 30 or lower.

A zoom lens system comprising, from the object side to the image side:

• a first lens unit of a positive refractive power;
• a second lens unit of a negative refractive power;
• and
• a third lens unit of a positive refractive power, wherein said third lens unit is a doublet lens element consisting of, from the object side to the image side, a negative lens element and a positive lens element and having two aspherical surfaces on its object and image sides;
• and wherein at least said second and third lens units shift on an optical axis of said zoom lens system during the zooming operation, and wherein all of said lens units include at least one high dispersion lens element having a refractive power opposite to that of the lens unit with an Abbe number of approximately 30 or lower.

A zoom lens system comprising, from the object side to the image side:

• a first lens unit of a positive refractive power, said first lens unit including a negative meniscus lens element convex to the object side;
• a second lens unit of a negative refractive power, said second lens unit including a positive high dispersion lens element with an Abbe number of approximately 30 or lower;
• and
• a third lens unit of a positive refractive power, said third lens unit including a positive lens element located on the object side end and another positive lens element located on the image side end;
• and wherein at least said second and third lens units shift on an optical axis of said zoom lens system during the zooming operation, and said zoom lens system fulfills the following condition:
• 13<(.o slashed.II.vertline./.o slashed.I).multidot.(Y'/f.sub.W).multidot.Z<28
• wherein:
• .o slashed.I represents the refractive power of said first lens unit;
• .o slashed.II represents the refractive power of said second lens unit;
• f.sub.W represents the shortest focal length of said zoom lens system;
• Y' represents the effective image height;
• and
• Z represents the zoom ratio.

A zoom lens system comprising, from the object side to the image side:

• a first lens unit of a positive refractive power, said first lens unit consisting of, from the object side to the image side, a negative meniscus lens element convex to the object side and two positive lens elements;
• a second lens unit of a negative refractive power, said second lens unit consisting of, from the object side surface to the image side, a negative lens element whose image side surface has a stronger refractive power than its object side surface, a biconcave lens element and a positive lens element;
• and
• a third lens unit of a positive refractive power, said third lens unit consisting of a first sub unit having a positive refractive power and a second sub unit located on the image side of the first sub unit and including a negative high dispersion lens element with an Abbe number of approximately 30 or lower, and said third lens unit consisting of three or four lens elements;
• and wherein at least said second and third lens units shift on an optical axis of said zoom lens system during the zooming operation.

A zoom lens system comprising, from the object side to the image side:

• a first lens unit of a positive refractive power;
• a second lens unit of a negative refractive power;
• and
• a third lens unit of a positive refractive power, said third lens unit consisting of, from the object side to the image side, a positive lens element and a positive composite lens element of a negative high dispersion lens element whose image side surface has a stronger refractive power than the object side surface and a positive lens element, and said third lens unit has an aspherical surface at the image side end surface;
• and wherein at least said second and third lens units shift on an optical axis of said zoom lens system during the zooming operation, and wherein all of said lens units include at least one high dispersion lens element having an Abbe number of approximately 30 or lower and having a refractive power opposite to that of the lens unit.

A zoom lens system comprising, from the object side to the image side:

• a first lens unit of a positive refractive power;
• a second lens unit of a negative refractive power, said second lens unit consisting of, from the object side to the image side, a negative lens element whose image side surface has a stronger refractive power than its object side surface and a positive high dispersion lens element with an air space between the negative lens element and the high dispersion lens element, and said second lens unit has at least one aspherical surface;
• and
• a third lens unit of a positive refractive power;
• and wherein at least said second and third lens units shift on an optical axis of said zoom lens system during the zooming operation, and wherein all of said lens units include at least one high dispersion lens element having an Abbe number of approximately 30 or lower and having a refractive power opposite to that of the lens unit and fulfills the following condition:
• 0.20<.o slashed.I/.vertline..o slashed.II.vertline.<0.31
• .nu..sub.3 -.nu..sub.4 <20
• wherein:
• .o slashed.I represents the refractive power of said first lens unit;
• .o slashed.II represents the refractive power of said second lens unit;
• .nu..sub.3 represents the Abbe number of the negative lens element in said second lens unit with respect to the D line;
• and
• .nu..sub.4 represents the Abbe number of the positive high dispersion lens element with respect to the D line.

A zoom lens system comprising, from the object side to the image side:

• a first positive lens unit;
• a second negative lens unit consisting of, from the object side to the image side, a negative lens element whose image side surface has a stronger refractive power than its object side surface and a positive lens element;
• and
• and wherein both of the side surfaces of the negative lens element are spherical surfaces and the positive lens element has at least one aspherical surface.

A compact zoom lens system having a high zoom ratio of at least 6 comprising:

• a first lens unit of a positive refractive power;
• a second lens of a negative refractive power;
• and
• a third lens unit of a positive refractive power, said third lens unit consisting of, from the object side to the image side, a positive lens element and a negative lens element and having at least one aspherical surface;
• wherein at least said second and third lens units shift on an optical axis of said zoom lens system during the zooming operation, and wherein all of said lens units include at least one high dispersion lens element having a refractive power opposite to that of the lens unit with an Abbe number of approximately 30 or lower, and the respective lens units can be positioned to provide an angle of view of approximately 60 degrees.