Optical: systems and elements – Lens
Reexamination Certificate
1999-06-29
2001-09-04
Sugarman, Scott J. (Department: 2873)
Optical: systems and elements
Lens
C359S708000, C359S711000, C359S712000, C378S084000
Reexamination Certificate
active
06285506
ABSTRACT:
TECHNICAL FIELD
The present invention relates to novel methods of producing curved optical elements, in particular elements of extremely high precision, for use with soft and hard x-rays, ultraviolet, visible, and infrared radiation and the optical elements achieved by these methods.
BACKGROUND OF THE INVENTION
Curved surfaces are used in a number of applications including but not limited to doubly curved crystals for x-ray applications, mirrors for ring laser gyros, and substrates for single or multilayer thin films.
Doubly curved crystals are known to be useful as a focusing device for monochromatic x-ray or a wavelength dispersive device in an x-ray spectrometer. For example, a toroidal curved crystal can provide point-to-point focusing of monochromatic x-rays, and a crystal curved to an ellipsoid can be used as a broad energy x-ray detection device. Some of the prior art is described in U.S. Pat. No. 4,780,899 and U.S. Pat. No. 4,949,367. These devices, having crystals bonded on a smooth concave substrate by a very thin layer of adhesive, have the drawback that the smoothness of the crystal planes is strongly affected by irregularities of the bonding layer. The irregularities can result from the lack of initial uniformity of the bonding layer on the substrate, or can occur during mounting of the crystal even if the initial adhesive layer is highly uniform. Another drawback is that a carefully prepared substrate is required for each curved surface.
Thus, the present invention is directed to providing inexpensive high quality optical surfaces, and to methods of fabrication thereof.
SUMMARY OF THE INVENTION
Briefly summarized, the present invention comprises in one aspect an optically curved element which includes a backing plate having a supporting surface, and an adhesive layer disposed above the supporting surface of the backing plate. The adhesive layer has a minimum thickness x. A flexible layer is also provided and disposed above the adhesive layer. The flexible layer, which includes an optical surface having a desired curvature, has a thickness y, wherein x>y.
In another aspect, an optically curved element is provided which includes a flexible layer and an adhesive layer. The flexible layer, which has an optical surface of a desired curvature, has a thickness y. The adhesive layer, which is disposed on a main surface of the flexible layer other than the optical surface, has a minimum thickness x, wherein x>y.
In a further aspect, a method for fabricating an optically curved element using a mold having a curved surface is provided. The method includes: providing a flexible layer having an optical surface; providing a backing plate having a supporting surface and disposing the flexible layer between the supporting surface of the backing plate and the curved surface of the mold; applying an adhesive between the flexible layer and the supporting surface of the backing plate; and applying pressure to at least one of the backing plate and the mold to squeeze the adhesive and conform the flexible layer to the curved surface of the mold, thereby producing the optically curved element.
In a still further aspect, a method for fabricating an optically curved element is disclosed which includes: providing a backing plate having a supporting surface; providing an adhesive layer disposed above the supporting surface of the backing plate, the adhesive layer having a minimum thickness x; and providing a flexible layer disposed above the adhesive layer, the flexible layer comprising an optical surface, and conforming the optical surface of the flexible layer to a desired curvature, the flexible layer having a thickness y, wherein x>y.
In one specific embodiment of the present invention, the device is fabricated by providing an optically smooth flexible layer, securing the flexible layer to a surface of a mold having a desired optical doubly curved shape, providing an adhesive (wherein the method of securing the optical surface of the flexible layer to the mold prevents adhesive from contacting the surface of the mold), providing a backing plate on the adhesive and applying pressure to at least one of the backing plate and the mold to squeeze the adhesive and permanently conform the surface of the flexible layer to the surface of the mold, and thereafter, removing the mold to thereby produce the device.
To restate, provided herein is a novel curved optical element, and method of fabrication, that acquires its shape from a reusable mold. Advantageously, the optical surface of the flexible layer need not conform exactly to a supporting surface of a backing plate. Further, the backing plate can be removable from the rest of the optical element. Thus, an inexpensive optically curved surface can be fabricated in accordance with the principles of the present invention, i.e., because a reusable mold is employed, and since the backing plate curvature and surface finish are not critical. The use of a relatively thick epoxy layer allows the flexible layer to conform to a curved surface of the mold. As used herein, relatively thick means that the thickness of the adhesive layer is greater than the thickness of the flexible layer having the optical surface to be curved.
In accordance with the present invention, the smooth optical surface can be curved to any preselected geometry to comprise one of a convex surface, a concave surface, a toroidal surface, a parabolic surface, a spherical surface or an ellipsoidal surface. The optical surface can be a singularly curved surface or a doubly curved surface. When the flexible layer comprises a crystal having diffracting planes, the diffracting planes can be either inclined or parallel to the optical surface of the flexible layer.
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Z.W. Chen and D.B. Wittry, “Microprobe x-ray fluorescence with the use of point-focusing diffractors”, Appl. Phys. Lett. 71 (13), Sep. 29, 1997, 1997 American Institute of Physics, pp. 1884-1886.
Z.W. Chen and D.B. Wittry, “Microanalysis by monochromatoc microprobe x-ray fluorescence-physical basis, properties, and future prospects”, Journal of Applied Physics, vol. 84, No. 2, Jul. 15, 1998, 1998 American Institute of Physics, pp. 1064-1073.
Heslin Rothenberg Farley & & Mesiti P.C.
Radigan, Esq. Kevin P.
Sugarman Scott J.
X-Ray Optical Systems, Inc.
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