Abstract: A lens module has a magnified side and a reduced side having an imaging surface. The lens module includes a first, a second, and a third lens groups having positive refractive powers respectively. The first lens group includes a first and a second lenses. A value calculated by dividing a distance between a center of a surface of the first lens facing the magnified side and the imaging surface by the effective focal length of the lens module is greater than or equal to 1 and smaller than or equal to 3. The second lens group located between the first lens group and the reduced side includes a third and a fourth lenses. The third lens group located between the second lens group and the reduced side includes a fifth lens. Refractive powers of the first to the fifth lenses are negative, positive, positive, negative and positive, respectively.

Abstract: A projection lens includes a first lens group, a second lens group, and a third lens group. The first lens group is composed of a first lens. The first lens has a concave surface and a convex surface, and the concave surface of the first lens faces a reducing side of the projection lens. The second lens group has positive refractive power, and includes a second lens having positive refractive power and a third lens having negative refractive power. The second lens is a biconvex lens, and the third lens has a concave lens facing the reducing side. The third lens group is composed of a fourth lens, and the fourth lens has a convex surface facing a magnifying side of the projection lens. The first lens group, the second lens group, and the third lens group include at least two aspheric lenses.

Abstract: A lens module including a first lens group, a second lens group, a third lens group, and an aperture stop is provided. The first lens group disposed between a magnified side and a reduced side has a positive refractive power. The second lens group disposed between the first lens group and the reduced side has a negative refractive power. The third lens group disposed between the second lens group and the reduced side has a positive refractive power. The aperture stop is disposed between the first lens group and the second lens group. Additionally, the distance from a center of the second surface to a center of the third surface is L1, an effective focal length is f, and the lens module satisfies 0.4<L1/f<1.2.

Abstract: An image system adapted to a projection display apparatus includes a first lens group having a negative refractive power, a second lens group having a positive refractive power, an aspheric reflector, and a curved reflector. The second lens group includes an aspheric lens which is the nearest to the light valve in the second lens group. A material of the aspheric lens includes glass, the thermal-optical coefficient of the glass is between 1.0×10?6/K and 12.5×10?6/K, and the refractive index of the glass is between 1.482 and 1.847. The aspheric reflector is disposed front of the first lens group for reflecting the image beam passing through the first lens group and second lens group. The curved reflector is disposed above the first lens group for reflecting the image beam reflected by the aspheric reflector onto the screen. The image system has a good imaging quality.

Abstract: An illumination system including a beam splitter, a first lamp, a second lamp, a first reflector, a second reflector, and a light uniforming element is provided. The first and the second lamp emit a first beam and a second beam to the beam splitter, respectively. A part of the first beam reflected by the beam splitter and a part of the second beam passing through the beam splitter constitute a third beam, and the other part of the first beam passing through the beam splitter and the other part of the second beam reflected by the beam splitter constitute a fourth beam. The first reflector and the second reflector reflect the third beam and the fourth beam, respectively. The light uniforming element is disposed on transmission paths of the reflected third beam and the reflected fourth beam.

Abstract: An illumination system including a beam splitter, a first lamp, a second lamp, a first reflector, a second reflector, and a light uniforming element is provided. The first and the second lamp emit a first beam and a second beam to the beam splitter, respectively. A part of the first beam reflected by the beam splitter and a part of the second beam passing through the beam splitter constitute a third beam, and the other part of the first beam passing through the beam splitter and the other part of the second beam reflected by the beam splitter constitute a fourth beam. The first reflector and the second reflector reflect the third beam and the fourth beam, respectively. The light uniforming element is disposed on transmission paths of the reflected third beam and the reflected fourth beam.