Glass Aspheric Lenses Offer a Practical Solution for Bar-Code Scanners
Ruth A. Mendonsa
Bar-code scanning devices rely heavily on laser diode lighting systems to record data, and product designers are looking closely at ways to increase efficiency and reduce costs.
Circularizing the elliptical beam from a laser diode for precise focusing and then manipulating the beam size to obtain performance specifications are the critical issues in laser scanning. The traditional approach is to design a system using a series of spherical lenses, because aberration is inherent when using spherical surfaces, and correction must be made. In addition, a laser beam has a high divergence angle, and spherical lenses can refract light only at small angles before the aberration is introduced. So three or four elements are usually required to collimate or focus the light, making the system very costly.
One bar-code scanner manufacturer, seeking a less expensive, smaller and more precise design for its product, found a solution with glass aspheric lenses made by Geltech Inc. of Orlando, Fla. A glass aspheric lens at the laser diode source collimates the light and, with an aperture device, controls the beam size. Because Geltech's diffraction-limited lenses are molded using a high-precision glass-pressing technology developed at Corning Incorporated, the savings from lower tooling costs and high-volume capability are reflected in the cost of the lenses. In addition, the lenses' small size allowed the bar-code scanner manufacturer to reduce the size of its laser system, resulting in even more cost savings.
The result, said the manufacturer, is a smaller, less expensive product that performs better.
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