Optical waveguides – With optical coupler – Switch
Reexamination Certificate
2001-03-08
2004-04-13
Nguyen, Khiem (Department: 2839)
Optical waveguides
With optical coupler
Switch
C385S018000, C385S012000
Reexamination Certificate
active
06721471
ABSTRACT:
BACKGROUND
The development of optical switches, including fiber optic switches, has been a result of a need to avoid electrical power in certain control lines because electrical switches in such situations can, for example, cause explosions in an explosive atmosphere and shocks if in the presence of liquid. Many optical switches are known in the art. See, e.g., U.S. Pat. No. 3,999,074; U.S. Pat. No. 4,045,667; U.S. Pat. No. 4,315,147; U.S. Pat. No. 4,904,044; U.S. Pat. No. 4,704,656; U.S. Pat. No. 5,892,862; U.S. Pat. No. 5,046,806.
For some optical switches, for example those containing a mirror actuator, the coupling efficiency of the reflected light and, therefore, the effectiveness of the signal detection is sensitive to alignment problems. The mirror actuator mechanism typically locates the mirror surface parallel to and in very close proximity to the fiber face in order to maintain good efficiency. In systems in which there is a gap between an end of the fiber and the mirror, the surfaces of the fiber and mirror may be prone to contamination, which can lead to each of back scattering and contamination, which in turn can lead to loss of light and hence reduced efficiency. Back scattering at any of the other optical interfaces can create additional noise in the optical signal and require additional signal processing or detector compensation to accurately detect the state of the switch.
One way of reducing the effect of back-scattered light on detector performance is to use fluorescence, such as atomic or molecular fluorescence, to create an optical switch. The property of fluorescence is well known in the art. Generally, an electron of an elemental or molecular target absorbs incident electromagnetic energy, typically light photons (FIG.
10
), which transfers the energy of the photon to the electron. This raises the electron one or more energy level. This higher energy level is usually unstable. As the electron returns to the ground state it emits a new photon that has less energy than the original photon, which means that it has a longer wavelength of light than the photon absorbed. For example, a blue high energy photon can cause a red fluorescent photon. This change in energy levels between the original photon, which can be called illumination or excitation light, and the emitted photon is a characteristic property of a given compound and is known as the Stoke's shift (FIG.
11
). As used herein, the term fluorescence also refers to two-photon and multi-photon excitation, quantum dots, which are about nanometer sized crystals made from materials such as cadmium selenide that when excited by higher energy light will emit light of lower energy. The wavelength emitted is determined by the size of the nanocrystal. A larger crystal produces longer wavelength light and a shorter crystal produces shorter wavelength light. These materials are commercially available from Quantum Dot Corporation of Hayward, Calif. These materials are known in the art, and other methods of accepting light of one wavelength or wavelength band and emitting light at a detectably different wavelength or wavelength band are also included herein.
There has been a need for multi-state optical switches that can provide multiple wavelength or color-based return signals from a single wavelength or wavelength band impulse signal, as well as for other functions provided by characteristics of fluorescence, either fluorescence alone or in combination with reflectance. The present invention provides these and other related advantages.
SUMMARY OF THE INVENTION
The present invention provides methods and apparatus that comprise optical switches that take advantage of fluorescence to enhance sensitivity, speed or effectiveness. In some embodiments, the present invention provides a target area comprising at least one target surface comprising a fluorophore-containing target material, wherein the target surface comprises at least a first target area that provides a first fluorescent response when illuminated by excitation light and a second target area that provides a second light response when illuminated; the second response can be either reflectance light or fluorescent light, or other desired light response. The excitation light can be optically guided to the target via an optical fiber or other optical light guide. The switch can detect the resulting fluorescent light emitted from the target, for example by collecting the light into an optical fiber or other optical light guide and optically guiding it to the detector. The detector, which in this embodiment can include an operably connected computer, spectrometer, spectrograph or other optical analyzer, measures at least one of the relative intensity or wavelength of the response from the target, such as the induced fluorescence emission of the first target area, then determines the presence or type of the fluorescence.
The excitation light can be UV light, blue light, green light or other energy able to induce fluorescence in the target fluorophore; typically, such excitation light will be referred to herein as blue light.
In one embodiment, actuating the switch causes an optical fiber or other light guide to move relative to the target areas or the targets to move relative to the optical fiber. (The present invention comprises multiple aspects, features and embodiments; such multiple aspects, features and embodiments can be combined and permuted in any desired manner unless otherwise clear from the context.) This introduces different target areas, at least one of which is fluorescent, into the optical path. By detecting the difference(s) between the target areas, the apparatus and methods determine the state of the switch. The apparatus can then report the result or initiate an action that the switch controls.
In one embodiment the present invention provides switches that provide an excitation energy, transmit the excitation energy to the target, collect the emanated response light from the target, and transmit the emanated response light through an optical detector system, which can be in a controller, that detects the ratio of the intensities or other difference of one or more wavelengths or wavelength bands of the emitted response. The present invention can be used in any device for which an optical switch may be advantageous, including for example cars, airplanes, motorcycles, boats, other vehicles, medical equipment such as surgical pencils and controllers, electronic devices such as computers, telephones, and e-commerce related devices, manufacturing apparatus such as devices in production lines, lathes and molds, and household appliances.
Another embodiment of the invention provides a fiber optic, or other light guide, switching system which includes an optical switch mechanism having a movable actuator and a light guide such as an optical fiber or liquid light guide coupled at an end of the light guide to the actuator wherein the light guide conducts light from a light source to the end of the light guide at the optical switch mechanism. One or both of the actuator and the target is movable relative to each other so as to direct the light emitted by the light guide from one target area to another, such as one fluorescence to another. In one embodiment, the differing fluorescent properties in the switch are provided by a film, further preferably a flexible film, whose surface is conditioned to provide at least two different fluorescent surfaces. The film or other target can be positioned such that an end surface of the actuator or light guide abuts the film throughout its movement from one position to another. A detector detects light emitted from the film or other target material and returned by a light guide, which may or may not be the same light guide as the illumination light guide. The detector determines from which target area, such as from which fluorescent material, the return light was emitted.
Alternatively, or additionally, the switch can contain one or more mirrors, lenses, beam splitters or other beam control devices that can direct
Graybeal Jackson Haley LLP
Nguyen Khiem
Tidal Photonics, Inc.
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