Optical: systems and elements – Collimating of light beam
Reexamination Certificate
1999-08-31
2001-04-24
Epps, Georgia (Department: 2873)
Optical: systems and elements
Collimating of light beam
C359S626000
Reexamination Certificate
active
06222679
ABSTRACT:
FIELD OF INVENTION
The current invention relates to the focusing and aiming of free-space beams onto a target.
BACKGROUND OF THE INVENTION
The focusing and aiming of free-space beams onto a target is critical in such applications as fiber optics. It is often necessary to provide a long-range of travel for the focused beam while maintaining a small, undistorted spot and maintaining the average incidence angle within the angular tolerance of the target. Attempted solutions have failed to achieve all these objectives or do so in a manner that is inefficient or unwieldy.
For example, single lens launchers do not provide enough degrees of freedom to compensate for common fabrication errors. For instance, if the incoming beam is not centered on the target to begin with, all the light may not enter the target no matter how well the lens is adjusted in a single lens launcher. Two-lens launchers provide more degrees of freedom, but the angle cannot be adjusted independent of the position. The apparatus disclosed in U.S. Pat. No. 5,077,622, titled “Apparatus For Precision Focussing and Positioning of A Beam Waist On A Target” and issued Dec. 31, 1991 to Lynch et al, achieves high-resolution positioning, but requires at least seven separate adjustment axes and is difficult to fit in a compact package. Finally, tapered fibers reduce the resolution required by making the target bigger at the input and tapering down to the final size. In addition to being expensive, these are also less efficient since light is lost in the taper. Indeed, the larger the taper the more light is lost. Tapered fibers are also not useful for polarization-maintaining applications, since the taper scrambles the polarization of the light.
SUMMARY OF THE INVENTION
The current invention is a method and apparatus for precisely focusing and aiming onto a very small and/or angle restricted target. The apparatus comprises a lens surrounded by two parallel windows. These components may be available off the shelf. Even if they must be custom-made for a particular application, the windows are straightforward to fabricate. The first window is an orientation window that orients the beam through the lens and toward the target. The second window is a translation window that translates the focused spot across the target, correcting for any mis-alignment of the lens.
The adjustments of the apparatus are tilting of the two windows and longitudinal translation (focusing) of either the lens or the target. High efficiency and a small spot size can be achieved even if the alignment of the non-adjustable components is imperfect. The focused beam can be translated and tilted independently for the best alignment to the target. The apparatus provides a long range of travel while maintaining a small, undistorted spot. The apparatus can be made compact and rugged, for use in applications with limited space. Likewise, standard manipulators, such as flexure plates and screws, can be used to tilt the windows and focus the lens from the front of the apparatus. As compared to prior attempted solutions, the current invention requires a minimal number of adjustments to achieve precise alignment.
In another embodiment, the lens is also capable of tilting. Tilting the lens in addition to the translation window increases the distance the focused spot can be translated before coma significantly distorts the spot. This allows for a greater ability to correct the mis-alignment of the lens and the target.
REFERENCES:
patent: 3761157 (1973-09-01), Humphrey
patent: 5077622 (1991-12-01), Lynch et al.
patent: 5182671 (1993-01-01), Kitagishi et al.
patent: 5796531 (1998-08-01), Keneda et al.
Agilent Technologies
Epps Georgia
Seyrafi Saeed
Wu Jack H.
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