Multivariate optical computing, also known as molecular factor computing, is an approach to the development of

compressed sensing Compressed sensing (also known as compressive sensing, compressive sampling, or sparse sampling) is a signal processing technique for efficiently acquiring and reconstructing a signal, by finding solutions to underdetermined linear systems. This ...

spectroscopic instruments, particularly for industrial applications such as process analytical support. "Conventional" spectroscopic methods often employ

multivariate Multivariate may refer to: In mathematics * Multivariable calculus * Multivariate function * Multivariate polynomial In computing * Multivariate cryptography * Multivariate division algorithm * Multivariate interpolation * Multivariate optical c ...

and chemometric methods, such as multivariate calibration,

pattern recognition Pattern recognition is the automated recognition of patterns and regularities in data. It has applications in statistical data analysis, signal processing, image analysis, information retrieval, bioinformatics, data compression, computer graphics ...

, and

classification Classification is a process related to categorization, the process in which ideas and objects are recognized, differentiated and understood. Classification is the grouping of related facts into classes. It may also refer to: Business, organizat ...

, to extract analytical information (including concentration) from data collected at many different wavelengths. Multivariate optical computing uses an

optical computer Optical computing or photonic computing uses light waves produced by lasers or incoherent sources for data processing, data storage or data communication for computing. For decades, photons have shown promise to enable a higher bandwidth than the ...

to analyze the data as it is collected. The goal of this approach is to produce instruments which are simple and rugged, yet retain the benefits of multivariate techniques for the accuracy and precision of the result. An instrument which implements this approach may be described as a multivariate optical computer. Since it describes an approach, rather than any specific wavelength range, multivariate optical computers may be built using a variety of different instruments (including Fourier Transform Infrared ( FTIR)1 and Raman). The "software" in multivariate optical computing is encoded directly into an optical element spectral calculation engine such as an interference filter based multivariate optical element (MOE),

holographic grating A holographic grating is a type of diffraction grating In optics, a diffraction grating is an optical component with a periodic structure that diffraction, diffracts light into several beams travelling in different directions (i.e., different ...

liquid crystal tunable filter A liquid crystal tunable filter (LCTF) is an optical filter that uses electronically controlled liquid crystal (LC) elements to transmit a selectable wavelength of light and exclude others. Often, the basic working principle is based on the Lyot f ...

spatial light modulator A spatial light modulator (SLM) is an object that imposes some form of spatially varying modulation on a beam of light. A simple example is an overhead projector Transparency (projection), transparency. Usually when the term SLM is used, it means ...

(SLM), or digital micromirror device (DMD) and is specific to the particular application. The optical pattern for the spectral calculation engine is designed for the specific purpose of measuring the magnitude of that multi-wavelength pattern in the

spectrum A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a specific set of values but can vary, without gaps, across a continuum. The word was first used scientifically in optics to describe the rainbow of colors ...

of a sample, without actually measuring a spectrum. Multivariate optical computing allows instruments to be made with the mathematics of pattern recognition designed directly into an optical computer, which extracts information from light without recording a spectrum. This makes it possible to achieve the speed, dependability, and ruggedness necessary for real time, in-line process control instruments. Multivariate optical computing encodes an

analog Analog or analogue may refer to: Computing and electronics * Analog signal, in which information is encoded in a continuous variable ** Analog device, an apparatus that operates on analog signals *** Analog electronics, circuits which use analog ...

optical regression

vector Vector most often refers to: *Euclidean vector, a quantity with a magnitude and a direction *Vector (epidemiology), an agent that carries and transmits an infectious pathogen into another living organism Vector may also refer to: Mathematic ...

of a transmission function for an optical element. Light which emanates from a sample contains the spectral information of that sample, whether the spectrum is discovered or not. As light passes from a sample through the element, the normalized intensity, which is detected by a broad band detector, is proportional to the

dot product In mathematics, the dot product or scalar productThe term ''scalar product'' means literally "product with a scalar as a result". It is also used sometimes for other symmetric bilinear forms, for example in a pseudo-Euclidean space. is an alg ...

of the regression vector with that spectrum, i.e. is proportional to the concentration of the analyte for which the regression vector was designed. The quality of the analysis is then equal to the quality of the regression vector which is encoded. If the resolution of the regression vector is encoded to the resolution of the laboratory instrument from which that regression vector was designed and the resolution of the detector is equivalent, then the measurement made by Multivariate Optical Computing will be equivalent to that laboratory instrument by conventional means. The technique is making headway in a niche market for harsh environment detection. Specifically the technique has been adopted for use in the oil industry for detection of hydrocarbon composition in oil wells and pipeline monitoring. In such situations, laboratory quality measurements are necessary, but in harsh environments.

History

Although the concept of using a single optical element for analyte regression and detection was suggested in 1986, the first full MOC concept device was published in 1997 from the Myrick group at the University of South Carolina, with a subsequent demonstration in 2001. The technique has received much recognition in the optics industry as a new method to perform optical analysis with advantages for harsh environment sensing.Jones, C.M., Freese, B., Pelletier, M. et al. 2012. Laboratory Quality Optical Analysis in Harsh Environments. Presented at the SPE Kuwait International Petroleum Conference and Exhibition, The technique has been applied to Raman spectroscopy,

fluorescence spectroscopy Fluorescence spectroscopy (also known as fluorimetry or spectrofluorometry) is a type of electromagnetic spectroscopy that analyzes fluorescence from a sample. It involves using a beam of light, usually ultraviolet light, that excites the electro ...

,Priore, R.J. (2013). "OPTICS FOR BIOPHOTONICS: Multivariate optical elements beat bandpass filters in fluorescence analysis". Laser Focus World. 49 (6): 49–52.

absorbance Absorbance is defined as "the logarithm of the ratio of incident to transmitted radiant power through a sample (excluding the effects on cell walls)". Alternatively, for samples which scatter light, absorbance may be defined as "the negative lo ...

spectroscopy in the UV-Vis,Priore, R.J., Greer, A.E., Haibach, F.G. et al. 2003. Novel Imaging Systems: Multivariate Optical Computing in the UV-VIS. In Proc., IS&T's NIP19: International Conference on Digital Printing Technologies, Vol. 19, 906–910. New Orleans, Louisiana. NIR and

MIR ''Mir'' (russian: Мир, ; ) was a space station that operated in low Earth orbit from 1986 to 2001, operated by the Soviet Union and later by Russia. ''Mir'' was the first modular space station and was assembled in orbit from 1986 to&n ...

,Jones, C., Gao, L., Perkins, D. et al. 2013. Field Test of the Integrated Computational Elements: A New Optical Sensor for Downhole Fluid Analysis. Presented at the SPWLA 54th Annual Logging Symposium, New Orleans, Louisiana, 22–26 June. SPWLA-2013-YY.

microscopy Microscopy is the technical field of using microscopes to view objects and areas of objects that cannot be seen with the naked eye (objects that are not within the resolution range of the normal eye). There are three well-known branches of micr ...

, reflectance spectroscopy and

hyperspectral imaging Hyperspectral imaging collects and processes information from across the electromagnetic spectrum. The goal of hyperspectral imaging is to obtain the spectrum for each pixel in the image of a scene, with the purpose of finding objects, identifyi ...

. In the years since first demonstration, applications have been demonstrated for defence, forensics, monitoring of chemical reactions,Fratkin, M. 2008. On-Line Oil Quality Sensors. Presented at the CTMA Symposium, Baltimore, Maryland, 7–9 April. environmental monitoring, recycling, food and drug, medical and life sciences, and the petroleum industry.Jones, C. 2014. Optical Sensors Analyze Fluids In Situ. The American Oil and Gas Reporter September: 117–123.Eriksen, K.O. (Statoil), Jones, C.M., Freese, R. et al. 2013. Field Tests of a New Optical Sensor Based on Integrated Computational. Presented at SPE Annual Technical Conference and Exhibition, New Orleans, Louisiana, 30 September–2 October. SPE-166415-MS. The first published demonstration for use of MOC in the harsh environments, was 2012 with a laboratory study with temperatures from 150F to 350F and pressures from 3000psi to 20,000psi, followed in 2013 with field trials in oil wells.

References

{{Reflist Spectroscopy