Wideangle-range-covering zoom lens

Claim 2

A wideangle-range-covering zoom lens comprising: a first lens group having a negative refracting power; a second lens group having a positive refracting power, which is arranged coaxially with said first lens group and adjacent to said first lens group on a side thereof opposite to a subject; a third lens group having a positive refracting power, which is arranged coaxially with said second lens group and adjacent to said second lens group on a side thereof opposite to the subject; and a fourth lens group having a negative refracting power, which is arranged coaxially with said third lens group and adjacent to said third lens group on a side thereof opposite to the subject; wherein said lens groups are relatively moved in zooming from a wideangle end to a telephoto end such that a gap decreases between said first lens group and said second lens group, a gap increases between said second lens group and said third lens group, and a gap decreases between said third lens group and said fourth lens group, and wherein the following conditions are satisfied: 0.l<φ.sub.1,2T /φ.sub.T ; and φ.sub.1,2W /φ.sub.W <0.57; where φ 1 ,2T : a composite refracting power of the first lens group and the second lens group at the telephoto end; φ T : an overall refracting power at the telephoto end; φ 1 ,2W : a composite refracting power of the first lens group and the second lens group at the wideangle end; φ W : an overall refracting power at the wideangle end.

Claim 3

A wideangle-range-covering zoom lens according to claim 1, wherein the following conditions are satisfied: φ.sub.3,4T /φ.sub.T <0.8; and 0.16<φ.sub.3,4W /φ.sub.W ; where φ 3 ,4T : a composite refracting power of the third lens group and the fourth lens group at the telephoto end; φ T : an overall refracting power at the telephoto end; φ 3 ,4W : a composite refracting power of the third lens group and the fourth lens group at the wideangle end; φ W : an overall refracting power at the wideangle end.

Claim 4

A wideangle-range-covering zoom lens comprising: a first lens group having a negative refracting power; a second lens group having a positive refracting power, which is arranged coaxially with said first lens group and adjacent to said first lens group on a side thereof opposite to a subject; a third lens group having a positive refracting power, which is arranged coaxially with said second lens group and adjacent to said second lens group on a side thereof opposite to the subject; and a fourth lens group having a negative refracting power, which is arranged coaxially with said third lens group and adjacent to said third lens group on a side thereof opposite to the subject; wherein said lens groups are relatively moved in zooming from a wideangle end to a telephoto end such that a gap decreases between said first lens group and said second lens group, a gap increases between said second lens group and said third lens group, and a gap decreases between said third lens group and said fourth lens group, and wherein the following conditions are satisfied: β.sub.4 /β.sub.2 >1 and β.sub.2 >1 and β.sub.4 >1; where β 4 : an amount expressed by the following equation if β 4W and β 4T are use magnifications of the fourth lens group at the wideangle end and at the telephoto end, respectively: β 4 =β 4T /β 4W ; β 2 : an amount expressed by the following equation if β 2W and β 2T are use magnifications of the second lens group at the wideangle end and at the telephoto end, respectively: β 2 =β 2T /β 2W .

Claim 5

A wideangle-range-covering zoom lens comprising: a first lens group having a negative refracting power; a second lens group having a positive refracting power, which is arranged coaxially with said first lens group and adjacent to said first lens group on a side thereof opposite to a subject; a third lens group having a positive refracting power, which is arranged coaxially with said second lens group and adjacent to said second lens group on a side thereof opposite to the subject; and a fourth lens group having a negative refracting power, which is arranged coaxially with said third lens group and adjacent to said third lens group on a side thereof opposite to the subject; wherein said lens groups are relatively moved in zooming from a wideangle end to a telephoto end such that a gap decreases between said first lens group and said second lens group, a gap increases between said second lens group and said third lens group, and a gap decreases between said third lens group and said fourth lens group, and wherein the following conditions are satisfied: β.sub.4 /β.sub.2 >1 and β.sub.2 >1 and β.sub.4 >1; where β 4 : an amount expressed by the following equation if β 4W and β 4T are use magnifications of the fourth lens group at the wideangle end and at the telephoto end, respectively: β 4 =β 4T /β 4W ; β 2 : an amount expressed by the following equation if β 2W and β 2T are use magnifications of the second lens group at the wideangle end and at the telephoto end, respectively: β 2 =β 2T /β 2W .

Claim 6

A wideangle-range-covering zoom lens according to claim 3, wherein the following conditions are satisfied: φ.sub.3,4T /φ.sub.T <0.8; and 0.16<φ.sub.3,4W /φ.sub.W ; where φ 3 ,4T : a composite refracting power of the third lens group and the fourth lens group at the telephoto end; φ T : an overall refracting power at the telephoto end; φ 3 ,4W : a composite refracting power of the third lens group and the fourth lens group at the wideangle end; φ W : an overall refracting power at the wideangle end.