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Laser Beam Waist-Locating Device

IP.com Disclosure Number: IPCOM000044323D
Original Publication Date: 1984-Dec-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Heussmann, DW: AUTHOR [+4]

Abstract

When using converging laser beams, it is often necessary to accurately measure the location of the beam "waist" as measured along the beam axis. Means are described for measuring beam spot size at each edge of the beam cross-section and adjusting the position of the beam until the two spot sizes are equal. The technique assumes that the beam waist is then centered between the measuring locations. In the figure, laser 10 provides a collimated beam 11 which, when passed through a positive focal length lens 12, forms a focused beam 13. As is often the case for such an optical setup, one wishes to detect very accurately the waist location of the focused beam 13. Beam splitters 17 and 19 are placed into the beam path such that their spacing will allow for the straddling of the near field region of the beam.

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Laser Beam Waist-Locating Device

When using converging laser beams, it is often necessary to accurately measure the location of the beam "waist" as measured along the beam axis. Means are described for measuring beam spot size at each edge of the beam cross-section and adjusting the position of the beam until the two spot sizes are equal. The technique assumes that the beam waist is then centered between the measuring locations. In the figure, laser 10 provides a collimated beam 11 which, when passed through a positive focal length lens 12, forms a focused beam 13. As is often the case for such an optical setup, one wishes to detect very accurately the waist location of the focused beam 13. Beam splitters 17 and 19 are placed into the beam path such that their spacing will allow for the straddling of the near field region of the beam. Spot size measurements at 17 and 19 are preferably located in the far field regions of the beam. Splitter 18 is placed at the bisector of splitter 17 and 19 to allow for the measuring of the beam waist diameter. Spot-size detectors 14 and 16 receive their respective reflected beams from splitters 17 and 19, respectively, and are monitored as the waist-locating assembly is translated along the beam axis. When spot diameter readings from the detectors obtain equivalent readings, the waist location is read from scale 20. The waist diameter is obtained at this time through spot-size detector 15.

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