Fresnel lens based spectroscopic detector
AssigneeUnited Technologies Corporation
InventorsGary A. Ball, Richard A. Meinzer
Life of this patent
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Abstract
A detector for laser radiation that detects the presence of above-threshold radiation in one of a set of wavelength ranges employs a set of Fresnel lenses designed to focus radiation in a particular band onto a metal-coated film. A series of Fresnel lenses is designed with constant focal lengths, but each lens is designed to have that focal length at a specific wavelength. Only when the wavelength of the incident radiation matches the design wavelength of the Fresnel lens will the film be marked or machined. Radiation of differing wavelengths will be defocused to a degree that will reduce the intensity below the level that will mark or machine the film. An electronic based version of this spectroscopy detector can also be implemented.
Claims9
A device for detecting optical radiation, comprising:
- a lens array of at least one Fresnel lens in a first plane, each member of said array having a common predetermined focal length at a predetermined wavelength different from the other members, disposed on a first surface of said device, for intercepting optical radiation and focusing said intercepted optical radiation to an array of focal spots;
- and
- a detecting film disposed parallel to said array of at least one Fresnel lens, said detecting film disposed in a second plane separated from said first plane by said predetermined focal length and being formed from a predetermined material having a predetermined damage threshold for optical radiation wherein radiation emitted from said lens array carrying a sample intensity level exceeding said predetermined damage threshold for a certain dwell time.
A device for detecting optical radiation, comprising:
- a Fresnel lens disposed in a first plane, said lens having a predetermined focal length at a predetermined wavelength, disposed on a first surface of said device, for intercepting optical radiation and focusing said intercepted optical radiation to a focal spot;
- and
- a spatial aperture disposed in a second plane separated from said first plane by said predetermined focal length and aligned with said lens such that radiation focused at said second plane by said lens passes through said spatial aperture;
- an optical detector positioned behind said spatial aperture for generating a signal in response to radiation passing through said spatial aperture;
- and
- signal processing means connected to said optical detector for processing said signal therefrom.
Dependencies are inferred from the claim text.