Zoom lens and image projection apparatus having the same

An image projection apparatus, comprising:

• a display unit for forming an original;
• and
• a zoom lens for projecting the original formed by the display unit onto a surface to be projected,
• wherein the zoom lens is telecentric on a reduction side and comprises a plurality of lens units, wherein a smallest positive lens is defined as a positive lens whose hb/ha is smallest among a plurality of positive lenses in the zoom lens in at least a part of a zoom range from a wide-angle end to a telephoto end where ha represents a height of a paraxial marginal ray passing through the zoom lens and hb represents a height of a paraxial chief ray passing through the zoom lens, the zoom lens satisfies following conditions:
• νdp>75
• fw/fp<0.6
• where νdp indicates an Abbe constant of a material of the smallest positive lens, fp indicates a focal length of a lens unit including the smallest positive lens, and fw indicates a focal length of an entire system of the zoom lens at the wide-angle end.

An image pickup apparatus, comprising:

• a photoelectric converting element;
• and
• a zoom lens for guiding light from a subject onto the photoelectric converting element,
• wherein the zoom lens is telecentric on a reduction side and comprises a plurality of lens units, wherein a smallest positive lens is defined as a positive lens whose hb/ha is smallest among a plurality of positive lenses in the zoom lens in at least a part of a zoom range from a wide-angle end to a telephoto end where ha represents a height of a paraxial marginal ray passing through the zoom lens and hb represents a height of a paraxial chief ray passing through the zoom lens, the zoom lens satisfies following conditions:
• νdp>75
• fw/fp<0.6
• where νdp indicates an Abbe constant of a material of the smallest positive lens, fp indicates a focal length of a lens unit including the smallest positive lens, and fw indicates a focal length of an entire system of the zoom lens at the wide-angle end.

A zoom lens, which is telecentric on a reduction side, comprising a plurality of lens units,

• wherein a first negative lens whose effective diameter is smallest is disposed within a range of a length 0.6 L to a length 0.9 L from a first lens surface which is disposed at most enlargement side of the zoom lens at a wide-angle end when an overall lens length is L,
• wherein a smallest positive lens is disposed within a range of a length 0.2 L on an enlargement side of the first negative lens, and
• wherein the zoom lens satisfies following conditions:
• νdp>75,
• fw/fp<0.6,
• where νdp represents Abbe constant of material of the smallest positive lens, fp represents a focal length of a lens unit including the smallest positive lens, and fw represents a focal length of an entire system at the wide-angle end.

An image projection apparatus, comprising:

• a display unit for forming an original;
• and
• a zoom lens for projecting the original formed by the display unit onto a surface to be projected,
• wherein the zoom lens is telecentric on a reduction side and comprises a plurality of lens units,
• wherein a first negative lens whose effective diameter is smallest is disposed within a range of a length 0.6 L to a length 0.9 L from a first lens surface which is disposed at most enlargement side of the zoom lens at a wide-angle end when an overall lens length is L,
• wherein a smallest positive lens is disposed within a range of a length 0.2 L on an enlargement side of the first negative lens, and
• wherein the zoom lens satisfies following conditions:
• νdp>75,
• fw/fp<0.6,
• where νdp represents Abbe constant of material of the smallest positive lens, fp represents a focal length of a lens unit including the smallest positive lens, and fw represents a focal length of an entire system at the wide-angle end.

An image pickup apparatus, comprising:

• a photoelectric converting element;
• and
• a zoom lens for guiding light from a subject onto the photoelectric converting element,
• wherein the zoom lens is telecentric on a reduction side and comprises a plurality of lens units,
• wherein a first negative lens whose effective diameter is smallest is disposed within a range of a length 0.6 L to a length 0.9 L from a first lens surface which is disposed at most enlargement side of the zoom lens at a wide-angle end when an overall lens length is L,
• wherein a smallest positive lens is disposed within a range of a length 0.2 L on an enlargement side of the first negative lens, and
• wherein the zoom lens satisfies following conditions:
• νdp>75,
• fw/fp<0.6,
• where νdp represents Abbe constant of material of the smallest positive lens, fp represents a focal length of a lens unit including the smallest positive lens, and fw represents a focal length of an entire system at the wide-angle end.