Abstract: A zoom lens for imaging an image onto a photosensitive element includes a first lens group, a second lens group, a third lens group and a fourth lens group. The second lens group is located and suitable for moving between the first lens group and the third lens group; the fourth lens group is located and suitable for moving between the third lens group and the photosensitive element. The first lens group, the second lens group, the third lens group, and the fourth lens group have a positive refractive power, a negative refractive power, a positive refractive power and a positive refractive power, respectively. Besides, the third lens group includes at least a hybrid lens and the second lens group includes at least an aspheric lens, the number of the aspheric lens is smaller than or equal to 2. Thus, manufacturing cost of the zoom lens mentioned above is lower.

Abstract: A zoom lens suitable for imaging an object on a photosensitive device is provided. The zoom lens includes a first lens group, a second lens group, a third lens group and a fourth lens group, which are arranged in series. The fourth lens group is disposed near the photosensitive device. The second lens group and the third lens group are suitable for moving between the first lens group and the fourth lens group. The first lens group, the second lens group, the third lens group and the fourth lens group include at least a glass lens and a plurality of plastic lenses. The number of the plastic lenses is more than the number of glass lenses. Thus, overall cost of producing the zoom lens is lower.

Abstract: A zoom lens suitable for imaging an object on a photosensitive element is provided. The zoom lens includes a first lens group, a second lens group disposed between the first lens group and the photosensitive element, a third lens group disposed between the second lens group and the photosensitive element, and a fourth lens group. The second lens group is suitable for moving between the first lens group and the third lens group. The third lens group includes two lenses having positive refractive power. The fourth lens group is disposed and suitable for moving between the third lens group and the photosensitive element. The refractive powers of the first lens group, the second lens group, the third lens group, and the fourth lens group are a positive value, a negative value, a positive value, and a positive value respectively.

Abstract: A zoom lens for imaging an image onto a photosensitive element includes a first lens group, a second lens group, a third lens group and a fourth lens group. The second lens group is located and suitable for moving between the first lens group and the third lens group; the fourth lens group is located and suitable for moving between the third lens group and the photosensitive element. The first lens group, the second lens group, the third lens group, and the fourth lens group have a positive refractive power, a negative refractive power, a positive refractive power and a positive refractive power, respectively. Besides, the third lens group includes at least a hybrid lens and the second lens group includes at least an aspheric lens, the number of the aspheric lens is smaller than or equal to 2. Thus, manufacturing cost of the zoom lens mentioned above is lower.

Abstract: An illumination system for a projector includes a light source, a light valve and a movable lens set between the light source and the light valve. The movable lens set has lenses whose relative positions are alterable manually or automatically depending on different input source thereby to adjust the illumination area of the illumination system on the light valve so that the light source can converge light projection on the active area of the light valve without wasting the light source. And the optical structure of the illumination system does not have to be redesigned or changed for different resolution of light valve. Production cost of the illumination system of the projectors can be reduced.

Abstract: A zooming lens is suitable for projecting images produced by a display device onto a screen. The zooming lens includes a first set of lenses and a second set of lenses, wherein the second set of lenses is disposed in the optical path between the first set of lenses and the display device. The first set of lenses includes first lens, second lens, third lens, and fourth lens sequentially, and the fourth lens is adjacent to the second set of lenses. The second set of lenses includes fifth lens, sixth lens, seventh lens, and composite lens sequentially, and the composite lens is adjacent to a side of the display device. The optical focusing of the lenses, from the first one through the seventh and to the composite lens, are positive, negative, negative, positive, positive, negative, positive value and positive, respectively. The composite lens includes two optical lenses.

Abstract: A zooming lens is suitable for projecting images produced by a display device onto a screen. The zooming lens includes a first set of lenses and a second set of lenses, wherein the second set of lenses is disposed in the optical path between the first set of lenses and the display device. The first set of lenses includes first lens, second lens, third lens, and fourth lens sequentially, and the fourth lens is adjacent to the second set of lenses. The second set of lenses includes fifth lens, sixth lens, seventh lens, and composite lens sequentially, and the composite lens is adjacent to a side of the display device. The optical focusing of the lenses, from the first one through the seventh and to the composite lens, are positive, negative, negative, positive, positive, negative, positive value and positive, respectively. The composite lens includes two optical lenses.