Patent ID: 6417972
Filing Date: 2002-07-09
Classification: G02B

Abstract:
A high-resolution variable focus lens system having an extra-long back focal length with telecentric design, comprising:three groups of lenses positioned between a screen and an imaging panel, including: a first group of lenses for zooming and focusing of the lens system, wherein the first group of lenses includes a first lens, a second lens and a third lens, and the first and the third lenses are positive lenses while the second lens is a negative lens, and the first group has a negative power in combination of the lenses; a second group of lenses for zooming of the lens system, wherein the second group of lenses includes a fourth lens and a fifth lens, the fourth lens is a negative lens, and the fifth lens is a positive lens, and the second group has a negative power in combination of the lenses; a third group of lenses for zooming of the lens system, wherein the third group of lenses includes a sixth, a seventh, an eighth, a ninth, a tenth and an eleventh lens, the sixth lens is a positive lens, the seventh lens is a negative lens, the eighth lens is a positive lens, the ninth lens is a negative lens, and the tenth and the eleventh lenses are positive lenses, and the third group has a positive power in combination of the lenses; wherein the focal length of the lens system can be changed by varying a distance between the first group and the second group of lenses as well as the second group and third group of lenses along the optical axis, and furthermore, the variable focus lens system satisfies conditions as follows: 2.15fW&lE;|f1|&lE;2.89fW;â€ƒâ€ƒ(1) 4.86fW&lE;|f2|&lE;9.82fW;â€ƒâ€ƒ(2) â€ƒ1.65fW&lE;f3&lE;1.74fW;â€ƒâ€ƒ(3)0.37f3&lE;t12&lE;0.42f3;â€ƒâ€ƒ(4) andN6&gE;1.66;â€ƒâ€ƒ(5) where f1 to f3 are focal length of the first, the second and the third group of lenses, respectively, fW is a focal length of the variable focus lens system in wide angle configuration, t12 is the axial distance between the sixth lens and the seventh lens and N6 is the refractive index of the sixth lens.