Fixed-Ratio Upcollimators
U.S. Laser upcollimators (also called beam expanders), are used to alter the beam divergence and diameter of a given laser beam, primarily to achieve smaller focused spot sizes. While the beam diameter expands at the ratio of the upcollimator, the beam divergence is simultaneously reduced by the reciprocal of the ratio. The product of the diameter and divergence (the optical invariant) however, remains constant. Upcollimators are also useful in expanding the diameter of a laser beam to reduce its intensity at an optical surface, thus reducing the possibility of optical damage. The U.S. Laser upcollimator is of the Galilean design, using a negative input element and a positive output element. This design is advantageous for laser use in that the combination of negative and positive elements inherently produces lower optical aberrations, and unlike the Keplerian designs, does not focus the beam internally between the elements. All optics used in the U.S. Laser upcollimators are fabricated from the highest quality laser grade fused silica for maximum damage resistance, and are highly damage resistant anti-reflection coated to minimize Fresnel (surface) losses. Lenses are mounted in a black anodized aluminum barrel, which has adjustment capability to optimize lens spacing. The standard mount is adjustable in three axes, one axis of translation about the beam axis, and two axes of tilt. The upcollimator assembly comes preadjusted, and is provided mounted on a standard U.S. Laser carriage mount. Standard A/R coating is for use at 1064 nm. Input beam diameter 12 mm (max). Output beam diameter 40 mm (max). Consult sales department for coatings at other wavelengths.
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