Unlike a conventional spherical lens, a "cylinder lens" has curvature along only one axis, as shown in the first figure. Cylinder lenses are useful in applications where light needs to be manipulated in only one direction. The example shown is a plano-convex positive lens, which brings parallel rays to a line focus.
Cylinder lenses are often used for beam shaping. A beam's "shape" refers to the brightness of the beam's cross section perpendicular to the beam's direction of travel. Cylinder lenses are particularly useful for beam shaping because they can alter the beam shape in two dimensions independently. The following are three examples for which cylinder lenses are best suited.
- Line generators: A primary application of cylinder lenses is expanding a beam of light into a two-dimensional "fan" shape. The fan creates a line when it illuminates an object. Barcode scanners and laser levels are examples of instruments that use cylinder lenses as line generators.
- Side-emitting diode laser collimators: Side-emitting diode lasers have a rectangular aperture. Because of this asymmetry, the emitted beam is astigmatic, meaning that the beam expands at different rates along the horizontal and vertical axes. Because a cylindrical lens focuses light along only one axis, such a lens can correct the mismatched focal lengths, yielding a circularly symmetric beam.
- Anamorphic illumination: It can be wasteful to illuminate a rectangular region of an object by blocking out the unwanted light from a circular beam. A pair of crossed cylindrical lenses in sequence can create a region of rectangular illumination with less loss of light. Rectangular illumination of this type has found application in street lighting.
Although cylinder optics present unique opportunities, incorporating them and optimizing performance present some unique design challenges. Ross offers a range of difficult-to-find cylinder optics, and our optical engineers can help you make the best choices for your design. Furthermore, should your project require unusual curvatures or dimensions, we have the capacity to provide custom-fabricate cylinder.
Give us a call at 1-800-880-5417 to talk to one of our engineers about your project and learn how we can help make it successful.
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