d4diddy, in publishing your opinion regarding CDEX combining two techniques and referencing a press release, you've caused me to adopt an opinion that when it comes to CDEX and their unique technology applications, you might consider reading more of the technical documentation provided.
A prime example follows, and you will likely note with great interest (based upon your publshed thoughts regarding CDEX combining TWO proceses) that they document THREE (3) processes being employed in 2012 with their Enhanced Photoemission Spec (EPS) and they also use the word: unique.
One(1) Fluorescence....The first process involves a wavelength shift that is due to an energy transfer from the incident photons...the resultant photon flux emission is referred to as fluorescence, although luminescence, phosphorescence, and photoluminescence are frequently used to describe these processes as well.
Two(2) Raman scattering. The second process involves scattering of the incident energy by the target material due to its vibrational state; this process is known as Raman scattering
Three (3) Specular Reflection or Absorption. The third component of EPS involves specular reflection or absorption from the surface of the target material so that only selective portions of the incident energy spectrum are reflected, while others are absorbed.
At least this is what I read from CDEX in the US Patent & Trademark Office Patent Application Database
United States Patent Application 20120056093 Kind Code A1 Poteet; Wade ; et al. March 8, 2012
-------------------------------------------------------------------------------- Substance detection, inspection and classification system using enhanced photoemission spectroscopy
Abstract A handheld or portable detection system with a high degree of specificity and accuracy, capable of use at small and substantial standoff distances (e.g., greater than 12 inches) is utilized to identify specific substances and mixtures thereof in order to provide information to officials for identification purposes and assists in determinations related to the legality, hazardous nature and/or disposition decision of such substance(s). The system uses a synchronous detector and visible light filter to enhance detection capabilities.
[0003] Ultraviolet to Near Infrared ("UV to NIR") EPS is an analytical technique used to identify and characterize chemical and biological materials and compositions. Modern light sources and detectors have made true handheld operation (as opposed to "transportable") possible, and unique signal processing techniques increase sensitivity of these systems to allow detection of trace amounts of materials on surfaces. In operation, UV to NIR EPS systems direct energy (in the form of concentrated photons) from an excitation source toward a target area using, for example, reflective or refractive optics. Photoelectric and other interactions of the photons with the sample material produce detectable wavelength-shifted emissions that are typically at longer wavelengths than the absorbed excitation UV to NIR photons, and specular reflection or absorption produces selected wavelength-specific portions of the originating energy.
[0004] The first process involves a wavelength shift that is due to an energy transfer from the incident photons (at a specific wavelength) to the target materials. The transferred energy causes some of the sample's electrons to either break free or enter an excited (i.e., higher) energy state. Thus, these excited electrons occupy unique energy environments that differ for each particular molecular species being examined.
[0005] As a result, electrons from higher energy orbital states "drop down" and fill orbitals vacated by the excited electrons. The energy lost by the electrons going from higher energy states to lower energy states results in an emission spectrum unique to each substance. When this process occurs in a short time, usually 100 nanoseconds or less, the resultant photon flux emission is referred to as fluorescence, although luminescence, phosphorescence, and photoluminescence are frequently used to describe these processes as well.
[0006] The second process involves scattering of the incident energy by the target material due to its vibrational state; this process is known as Raman scattering, and occurs in a relatively narrow band of wavelengths that result from the incident energy being in the correct range to excite the phenomenon. The third component of EPS involves specular reflection or absorption from the surface of the target material so that only selective portions of the incident energy spectrum are reflected, while others are absorbed.
[0007] The resultant emission spectrum generated is detected with a spectrograph, digitized and analyzed (i.e., wavelength discrimination) using unique algorithms and signal processing. Each different substance within the target area produces a distinctive spectrum that can be sorted and stored for comparison during subsequent analyses of known or unknown materials.
[0008] UV to NIR EPS does have some drawbacks. First, it can be affected by interference (or clutter). Interference is defined as unwanted UV to NIR flux reaching the detector that does not contribute directly to the identification of a material of interest. For example, when attempting to detect illegal substance on clothing, clutter can arise from exciting unimportant molecules in the target area, exciting materials close to the detector/emitter region, external flux from outside the target area (including external light sources like room lights or the sun) and scattering from air and/or dust in the light path.
[0009] UV to NIR EPS systems also are limited in terms of sensitivity distances. Greater distances between the substance of interest and the UV to NIR excitation source and detector result in weaker return photon flux (i.e., weaker, if any, EPS) from the sample material.
[0010] Conventional spectroscopy and detection techniques include, among other things, neutron activation analysis, ultraviolet absorption, ion mobility spectroscopy, scattering analysis, nuclear resonance, quadrupole resonance, near infrared (NIR) reflectance spectroscopy, selectively-absorbing fluorescent polymers, and various chemical sensors. Each of these methodologies, however, suffers from deficiencies.
[0011] For example, neutron activation analyses, while capable of directly measuring ratios of atomic constituents (e.g., hydrogen, oxygen, nitrogen, and carbon) require bulky energy sources that have high power demands and thus do not lend themselves to handheld instruments. Traditional UV to NIR absorption and scattering techniques are subject to high degrees of inaccuracy (i.e., false alarms and omissions) absent sizeable reference resources and effective predictive analysis systems. Scattering analysis techniques suffer similar shortcomings.
[0012] Ion mobility spectroscopy devices are currently in use at many airports for "wiping" analysis, but suffer from low sensitivities in practical measuring scenarios and have high maintenance demands. Resonance Raman is an emerging and promising technology, but requires special surfaces and sample preparation for operation. Quadrupole resonance techniques offer a good balance of portability and accuracy, but are only effective for a limited number of materials (i.e., they have an extremely small range of materials they can reliably and accurately detect). These systems also suffer from outside interfering radio frequency sources such as terrestrial radio broadcast stations.
[0013] Finally, chemical sensors such as conventional NIR devices, while very accurate, are slow acting, have extremely limited ranges, and are too bulky for convenient handheld operation. Furthermore, chemical vapor sensors do not always produce consistent results under varying environmental conditions (e.g., high humidity and modest air currents) when substantial standoff distances are involved.
SUMMARY OF THE INVENTION
[0014] The invention relates generally to the field of substance and material detection, inspection, and classification at wavelengths between approximately 200 nm and approximately 1800 nm. In particular, a handheld Enhanced Photoemission Spectroscopy ("EPS") detection system with a high degree of specificity and accuracy, capable of use at small and substantial standoff distances (e.g., greater than 12 inches) is utilized to identify specific controlled substances and their mixtures in order to provide information to officials so that determinations can be made as to the legality and/or hazardous nature of such substance(s).
[0015] Thus, the invention relates to a handheld system, process, and method for material detection, inspection, and classification. In particular, the invention includes a miniature electronic scanning detection system (e.g, an EPS spectrograph) with a high degree of specificity and accuracy, operating generally in the ultraviolet to near infrared portion of the electromagnetic spectrum that is used to identify specific individual and unique mixtures of substances (including remote, real-time measurements of individual chemical species in complex mixtures).
[0016] The unique spectral emissions from common controlled substances allow the process to be applied to materials such as narcotics, illicit drugs, explosives, and toxic chemicals have also been observed with models of this instrument. The substances may additionally include food types, synthetic drugs, prescribed narcotics, liquids, powders and the like.
[0017] The invention provides a highly specific detection approach that directly addresses two major classes of technical challenges: (1) standoff detection of low levels of substance deposition on or under a variety of surfaces in highly variable circumstances with (2) an extremely low false alarm rate.
[0018] Miniaturizing an EPS detection system to a handheld unit sizes involves significant technological and engineering improvements over presently available spectrometer systems and light sources. For example, recently developed and commercially available light emitting diodes (LED's) can provide the necessary illumination and a bandpass filter of the proper wavelength can be utilized in front of the LED, so that only the molecules of interest are excited (the physical beam pattern of these LED's is such that two LED's, rotated so that their beam patterns are orthogonal to other, may be used for uniform illumination of the target of interest).
[0019] Additionally, the miniaturization of spectrometer components usually reduces overall sensitivity, so in order to increase the system sensitivity to the required level for trace detection of materials, a low-pass spectral filter (such as that illustrated herein) can be introduced into the receiving optical path prior to the spectrometer. This introduction of a low-pass spectral filter reduces unwanted light from the external environment, e.g., sunlight reduction for the UV implementation of this invention, as well as narrows the spectral bandwidth to improve the signal to noise ratio. Increases in signal to noise ratio can also be realized from suitable digital filtering techniques.
[0020] Further, modulating the light source(s) and utilizing phase sensitive (synchronous) detection along with advanced algorithms further improves the signal to noise ratio, which is directly related to the limit of minimum detection as well as the false positive rate. Improved signal to noise ratios, along with additional signal processing (algorithms include, but are not limited to, correlation, matched filters, mean squared error, and likelihood ratio comparisons) enhances detection as well.
[0021] The invention includes a handheld EPS detections system including (a) a miniature scanning detection system operating in the ultraviolet to near infrared portion of the electromagnetic spectrum that includes (i) an excitation light source; (ii) a bandpass filter; (iii) a low-pass spectral filter; and (iv) an ultraviolet fluorescence detector; (b) a processor coupled to the ultraviolet fluorescence detector, the processor receiving spectral data from the ultraviolet fluorescence detector; and (c) a database coupled to said processor that includes signature data for a plurality of predetermined chemical substances.
[0022] In another aspect, the invention includes an EPS detection system that can include a concentrator including a vacuum device (e.g., portable vacuum cleaner) operatively coupled to the EPS detections system with filter material over the intake to draw particles from the environment surrounding the area of interest and where a filter is then used as the target. This arrangement facilitates detection of airborne particles of the material of interest.
[0023] In another aspect, the EPS detection system of the invention emits light from single or multiple light sources, such as from an LED, laser, laser diode or flashlamp, to excite emission in different substances as well as exciting different emissions in the same substance. The light source may be pulsed, square-wave modulated, and/or continuous wave and may include single and/or multiple sources for complete scene illumination (e.g., rotate LED's, etc.).
[0024] In another aspect, the EPS detection system of the invention gathers spectral signatures with a spectrally selective detector, including conventional spectrometers, spectrally filtered photodetectors, spectrometers using Multimodal Multiplex Spectroscopy.TM., or any other form of spectral detection. In another aspect, the EPS detection system of the invention digitizes the obtained spectral signatures.
[0025] In another aspect, the EPS detection system applies unique algorithms for signal processing, including, but not limited to, embedded processors using filtered FFT, synchronous detection, phase-sensitive detection, digital filters unique to each particular substance being detected. It is important to note that one, two, or all three physical processes (photoemission, Raman scattering, or specular reflection or absorption) may be present in a particular detection scenario. When only total return energy in a specific band of wavelengths is being utilized to detect the target material, then all three processes produce the total measured spectral energy in the wavelength band and the total return signal amplitude in a range of wavelengths can produce the desired signal for analysis and display.
[0026] When more specificity is required, a frequency-space data transformation following digitization (e.g., FFT) allows the influence of each of the three processes to be separated by examining the individual coefficients of the transform series. Because certain coefficients are affected more by one process than another in this type of transform, deconvolution of the process creating the overall spectrum is possible.
[0027] In another aspect, the EPS detection system of the invention uses algorithms to compare the obtained spectral signatures to a database of known and/or previously obtained spectral signatures. These algorithms can include, but are not limited to, correlation, matched filters, mean squared error, Laplace transforms, Fourier transforms, least-squares, or likelihood ratio tests.
[0028] In another aspect, the EPS detection system of the invention displays the obtained spectral signatures and/or the results of a comparison of the obtained spectral with signatures to a database of known and/or previously obtained spectral signatures. In another aspect, the EPS detection system of the invention includes a handheld and/or battery operated device EPS detection device. In another aspect, the EPS detection system of the invention includes a GPS locater internally mounted within the EPS detection system and/or in a handheld component of such system.
[0029] In another aspect, the EPS detection system of the invention determines the distance to target in order to keep the system within a sensitive range and could adjust the detection threshold as a function of distance. In another aspect, the EPS detection system of the invention communicates wirelessly to a remote location. In another aspect, the EPS detection system of the invention includes cell phone and/or other remote access communications capabilities, including video functions and storage.
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