Abstract: A compact zoom lens system includes, from the object side to the image side, a negative first lens group (1), a positive second lens group (2), a positive third lens group (3) and a positive fourth lens group (4). The first lens group is stationary, and both the second and third lens groups are movable for effecting focal length change. The fourth lens group is also movable to compensate for image plane shift due to focal length change and thereby maintain the position of the image plane. The compact zoom lens system has a significantly reduced lens count and thus has an overall length of only 20 mm while achieving an approximately 3× zoom ratio. Sufficient back focal length is ensured even for such a short overall length. By employing aspheric lenses (10, 20, 301, 31, 41) for aberration correction, a high level of optical performance can be ensured.

Abstract: A compact imaging lens system consists of a first positive aspheric lens element (1) on the object side and a second negative aspheric lens element (2) on the image side. The first lens element is a meniscus lens convex toward the image side, whereby the incident light beam can be diverged by the first concave surface (11) of the first lens element, and thus a wide area of the second convex surface (12) of the first lens element can be illuminated by the divergent light beam. The second negative aspheric lens element is provided mainly for correcting chromatic aberration and off-axis aberration.

Abstract: A compact lens system includes, in succession from an object side to an image side, an aspheric first lens element (1) having a positive power, an aperture stop (4), an aspheric second lens element (2) having a negative power, and a third lens element (3) having a positive power. Both the first and second lens elements are meniscus lenses made of plastic, and the third lens element is a biconvex lens or a plano-convex lens made of glass. The first lens element has a convex surface (10) facing the object side and an opposite concave surface (11) facing the aperture stop. The second lens element has a concave surface (21) facing the aperture stop and an opposite convex surface (20) curved toward the image side. The surface (30) of the third lens element facing toward the image side has a radius of curvature larger than that of the other surface (31) facing the second lens element.

Abstract: A compact zoom lens includes, from the object side to the image side, a negative first lens group (1), a positive second lens group (2) and a positive third lens group (3). The first lens group is stationary, and both the second and third lens groups are movable along the optical axis. The compact zoom lens is zoomed by varying the distance between the first and second lens groups, and the focal length is adjusted by varying the distance between the second and third lens groups. The zoom lens is composed of only four single lenses in three groups, of which three (10, 31, 32) are plastic aspheric lenses and one (20) is a glass spherical lens.

Abstract: A laser level includes a laser light source adapted to emit a laser beam, a beam-splitting unit splitting the laser beam into a number of light beams along multi different directions and a beam-outgoing unit dispersing the number of light beams to form corresponding number of horizontal sector-shaped output beams. These sector-shaped output beams together form an output beam having an angle approximately of 360 degrees.