Optical waveguides – Optical waveguide sensor
Reexamination Certificate
2001-11-09
2004-11-16
Kim, Ellen E. (Department: 2874)
Optical waveguides
Optical waveguide sensor
C385S032000
Reexamination Certificate
active
06819811
ABSTRACT:
FIELD OF INVENTION
This invention is in the field of nano-size gas sensors that employ photons to interact with the sensing material in some way. This nano-technology includes the use of photon absorption, refraction, reflection and optical evanescence. The invention incorporates a sensing media, which comprises a chemical complex outside and/or immediately adjacent to a photon source and/or waveguide, e.g., a chemical media that changes its optical properties in response to gases and vapors. There are a number of applications where nano-scale sensors employ evanescent coupling from a waveguide to a porous coating containing a chemical that reacts with a gas or vapor to cause a change in the photon signal through the waveguide. This evanescent method can provide very fast CO response to even low levels of target gases and is also a valuable method to detect a variety of gases that can react with a thin layer coated onto a waveguide. In addition, the nano-scale sensors can be used to employ a multi-pass photon chamber or an optical switch that employs a change to the index of refraction of the sensor to move photons from one waveguide to another. There are other nano-technology sensing methods that can be used to make gas sensor; however, this invention deals with the optical method in the broad sense that photons are used. These optical methods include some interaction of the photons with matter, a photon emitter, a photon detector and a miniature sensor system.
BACKGROUND OF THE INVENTION
In recent years, a number of MEMS and MOEMS devices have been developed. These miniature machines and electro-optical devices may be fabricated using the photolithography techniques developed for silicon devices, such as turbines, switches, sensors and actuators. The macro-machining industry is in its infancy as was the silicon integrated circuit (IC) device industry 40 years ago. As design tools made possible the development of the IC industry, design tools are beginning to give today's researchers the opportunity to design new components combining the physical world needs of sensing and actuators with the rapidly growing capabilities of information technology.
In 1994, Quantum Group proposed to DOE STTR (94-1) the “Evanescent Detection of Gases”. This document was proprietary and not a public disclosure, but turned out to be a prescription for a new and better evanescent sensing method, which has been recently reduced to practice. The proposed evanescent system was designed to detect gases such as CO, H2, D2, T2, H2S, NO
x
, UF6, F2, PuF6, CI2 and ammonia.
One application of these proposed miniature evanescent sensors is to detect clandestine nuclear or chemical weapon facilities. Other applications are to monitor plumes from existing facilities, measure gases to control engines, fuel cells and other processes, environmental monitoring, safety and detect terrorist activities.
This proposal extends the well-known evanescent fiber optic sensor for detection of various ions in the liquid and gaseous phases (Harrick 1987: Mirabella 1985, Paul 1987; Simhony 1988 and Ruddy et al 1990; S. Shilov et al Proceedings of SPIE Vol. 3918 (2000) and Holmquist 1993). Bell aid Firestone (1986) and others (1985) have stated that many fiber optic systems can convey photon signals with nearly zero attenuation (losses).
Airborne gases and vapors such as hydrocarbons, NO
x
, hydrogen, carbon monoxide, nerve and mustard agents as well as other gaseous and vapors are generally detected by various instruments in the lab and field. Until very recently, this equipment was very large and expensive. The US government and many companies have embarked on methods to increase the speed of detection and to reduce the size of the detectors. The advent of MEMS and MOEMS has made possible the miniaturization of various sensors. In addition, chemioptical methods developed by Quantum Group in the 1980s have led to commercialization of very low powered biomimetic sensors in the 1990s.
Goldstein et al described examples of a CO sensing using biomimetic sensors, e.g., U.S. Pat. Nos. 5,063,164, 5,618,493, and patent application Ser. No. 09/487,512 filed Jan. 19, 2000, the contents of which are incorporated by reference. These biomimetic sensors mimic the human response to CO. This chemistry was an improvement of an earlier invention by Shuler and Schrauzer, i.e., U.S. Pat. No. 4,043,934. The Shuler and Schrauzer Patent also teaches the use of a chemistry with high copper ion concentration that converts CO to carbon dioxide even at room temperature, but has limited life and operates over a narrow range of relative humidity.
U.S. Pat. No. 5,063,164 teaches that in the presence of the target gas the danger from hazardous exposures may be determined by monitoring the sensor with a photon source, i.e., passing photons of a specific spectral region through the sensor and monitoring the intensity of the photon beam or using a pulsed photon source to conserve power with a simple photon detector such as a photodiode. There are a number of other target gas sensors that have been disclosed in U.S. Pat. Nos. e.g., Nos. 4,043,934, 5,346,671, 5,405,583, 5,618,493 and 5,302,350, which can detect a target gas such as CO by monitoring the optical properties of the sensor.
Goldstein described several CO detector systems which incorporate these type of optical changing sensors, such as the biomimetic sensor as discussed above, such as U.S. Pat. Nos. 5,280,273, and 5,793,295. Others such as by Marnie et al disclosed a low cost circuit (Apparatus) with software and method for detecting CO in U.S. Pat. Nos. 5,573,953 and 5,624,848. Goldstein et al further disclosed a digital and rapid regenerating means in co-pending patent applications Ser. Nos. 08/026,34 and 60/076,822 herein incorporated by reference. The SIR technology is described in a copending application Ser. No. 60/051,038 filed Jun. 27, 1998, which uses a sensor that responds to CO by a change in its optical properties, for example, as described in U.S. Pat. No. 5,063,164 and the improvement patents mentioned herein in example 1 and co-pending applications.
The gas detector systems include housings that contain one or more photon sources that emit photons in at least a region of the electromagnetic spectrum, a sensor that absorbs photons proportional to the CO exposure, a photodetector sensitive in the corresponding active region of the spectra, a circuit designed to measure the response, a noise maker or other signal means which are actuated by the circuit and an enclosure. The housing (enclosure) has at least one opening to permit the sound to escape and the CO or other gas to enter. The detector also contains a sensor that may be permanent or may be configured with a battery for convenient replacement or may be mounted within the housing designed for easy replacement and with or without a convenient battery replacement means. Several systems were disclosed in U.S. Pat. No. 5,793,295 by Goldstein issued in Aug. 11, 1998 and is hereby incorporated by reference.
In addition, some preferred embodiments of this invention are portable and can be placed on the vehicles visor or other locations (e.g., pocket, belt, dash) while driving. However, the portable unit is easily removed for use in other location outside the vehicle such as for CO protection in the workplace by workers and/or by contractors, fire person, utility or other serviceperson, etc., or on forklifts and similar vehicles that do not have visors. These types of portable products may be operated on common batteries that can be easily replaced. The sensor system may be replace separately or with the battery. The most accurate detector system able to respond to less than 30 ppm CO contains sensor(s) that need to be replace occasionally (1 to 5 years).
Several low cost sensor systems are disclosed in U.S. Pat Nos. 5,063,164, 5,624,848 (Marnie et al), 5,618,493, (Goldstein et al), 5,280,273 (Goldstein), 5,793,295 (Marnie et at) and higher cost advanced systems are disclosed in co-pending applications Ser. No. 60/076,822 filed Mar. 4
Christie Parker & Hale LLP
Kim Ellen E.
Quantum Group Inc.
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