Open Source Spectrometer Lit Review[edit | edit source]
As follows is the chronological order of articles related to Open Source Spectrometer design. Current as of Q1 2014.
Spectrometer Design[edit | edit source]
Design and implementation of a high-resolution, high-efficiency optical spectrometer
Abstract: We present the design, implementation and testing of a high-efficiency, high-resolution transmission grating spectrometer for measurements of near-ultraviolet to visible-range spectra of light from an electron beam ion trap, where geometry is constrained. The system consists of two 5 in. diameter f/4.6 achromatic lenses, a 6 in. diameter transmission grating ion-beam etched in fused silica, and a thinned, backilluminated CCD detector. The simple design minimizes the number of optical components, each with optimal throughput and high efficiency. Using a 30 μm wide entrance slit, a resolving power (λ/Δλ) of 15 400 at λ≈3850 Å has been demonstrated. The features and limitations of the instrument have been explored and an in situ calibration technique for use on the Livermore EBIT-II and SuperEBIT electron beam ion traps has been developed. © 2002 American Institute of Physics.
Chirped holographic grating used as the dispersive element in an optical spectrometer
Abstract: We have developed a new design of optical spectrometer based on the use of a chirped holographic grating inscribed on a flat substrate. This type of grating has a surface modulation with a spatially varying period. The ability of the chirped grating to focus a beam is exploited to reduce significantly the physical dimensions of the instrument. Wavelength selection is achieved by a pure translation of the chirped grating. The properties of the chirped grating spectrometer have been characterized with different lasers and arc lamps and compared with those of two commercial spectrometers. A performance parameter has been defined, enabling the various instruments to be compared. © 2005 Optical Society of America
Cavity ring‐down optical spectrometer for absorption measurements using pulsed laser sources
Abstract: We have developed a technique which allows optical absorption measurements to be made using a pulsed light source and offers a sensitivity significantly greater than that attained using stabilized continuous light sources. The technique is based upon the measurement of the rate of absorption rather than the magnitude of absorption of a light pulse confined within a closed optical cavity. The decay of the light intensity within the cavity is a simple exponential with loss components due to mirror loss, broadband scatter (Rayleigh, Mie), and molecular absorption. Narrowband absorption spectra are recorded by scanning the output of a pulsed laser (which is injected into the optical cavity) through an absorption resonance. We have demonstrated the sensitivity of this technique by measuring several bands in the very weak forbidden b1Σg-X3Σg transition in gaseous molecular oxygen. Absorption signals of less than 1 part in 106 can be detected.
Digital optical spectrometer-on-chip
Abstract: A concept of digital optical spectrometer-on-chip is proposed and results of their fabrication and characterization are reported. The devices are based on computer-designed digital planar holograms which involves millions of lines specifically located and oriented in order to direct output light into designed focal points according to the wavelength. Spectrometers were fabricated on silicon dioxide and hafnium dioxide planar waveguides using electron beam lithography and dry etching. Optical performances of devices with up to 1000 channels for a central wavelength of 660 nm are reported.
Compact, Self-Contained Optical Spectrometer
Abstract: We describe the construction and performance of a self-contained, battery-operated, hand-held optical spectrometer. This unit contains an onboard optical excitation source, miniaturized monochromator, CCD detector, Peltier cooler, LCD display module, and microprocessor control. We demonstrate capabilities for qualitative fluorescence determinations and semiquantitative fluorescence and absorption measurements. Resolution is λ/δλ ≍ 1200 at 434 nm.
Densely folded spectral images of a CCD spectrometer working in the full 200–1000 nm wavelength range with high resolution
Abstract: A new charge-coupled device (CCD) spectrometer has been studied and constructed by using a two-dimensional CCD detector and an integrated grating consisting of 10 subgratings. Effective spectral images of 268 mm along the dispersion direction have been densely folded 10 times to cover the full 200–1000 nm working wavelength range without any mechanical moving elements. The results show that the system has a spectral resolution and acquisition time of better than 0.07 nm and less than 100 ms, respectively, in the entire spectral range after system calibration.
Design and testing of a white-light, steady-state diffuse reflectance spectrometer for determination of optical properties of highly scattering systems
Abstract: We present a steady-state radially resolved diffuse reflectance spectrometer capable of measuring the absorption and transport scattering spectra of tissue-simulating phantoms over an adjustable 170-nm wavelength interval in the visible and near infrared. Measurements in a variety of phantoms are demonstrated over the relevant range of tissue optical properties, and the accuracy of the instrument is found to be approximately 10% in both scattering and absorption. Monte Carlo simulations designed to test the accuracy of the instrument are presented that support the experimental findings.
[Ivan Avrutsky, Kalyani Chaganti, Ildar Salakhutdinov, and Gregory Auner. “Concept of a Miniature Optical Spectrometer Using Integrated Optical and Micro-Optical Components.” Optics Info Base, October 20, 2006. http://www.opticsinfobase.org/ao/abstract.cfm?id=116042.]
Abstract" Presents a design for a compact optical band spectrometer. Device uses very small diffraction elements and boasts a 2nm resolution in the visible band.
Acquisition of High Spatial and Spectral Resolution Video with a Hybrid Camera System
Abstract: We present a hybrid camera system for capturing video at high spatial and spectral resolutions. Composed of an red, green, and blue (RGB) video camera, a grayscale video camera and a few optical elements, the hybrid camera system simultaneously records two video streams: an RGB video with high spatial resolution, and a multispectral (MS) video with low spatial resolution. After registration of the two video streams, our system propagates the MS information into the RGB video to produce a video with both high spectral and spatial resolution. This propagation between videos is guided by color similarity of pixels in the spectral domain, proximity in the spatial domain, and the consistent color of each scene point in the temporal domain. The propagation algorithm, based on trilateral filtering, is designed to rapidly generate output video from the captured data at frame rates fast enough for real-time video analysis tasks such as tracking and surveillance. We evaluate the proposed system using both simulations with ground truth data and on real-world scenes. The accuracy of spectral capture is examined through comparisons with ground truth and with a commercial spectrometer. The utility of this high resolution MS video data is demonstrated on the applications of dynamic white balance adjustment, object tracking, and separating the appearance contributions of different illumination sources. The various high resolution MS video datasets that we captured will be made publicly available to facilitate research on dynamic spectral data analysis.
A micro-spectrometer with phase modulation array
Abstract: A micro-spectrometer with phase modulation array is investigated in this paper. The vital component of this micro-spectrometer is a micro-interferometer array, which is built on a charge-coupled device (CCD) or a complementary metal oxide semiconductor (CMOS). Each element of micro-interferometer array is formed by polymethyl methacrylate (PMMA) grooves with different depth. When we illuminate the surface of the interferometer array, different interference intensity distribution would be formed at the bottom of each micro-interferometer. Optical power of this interferometer can be measured by the pixels of CCD or CMOS. The data can be substituted into a linear system. By solving the linear system with Tikhonov regularization method, spectrum of the incident beam can be reconstructed. Simulation results prove that the detection range of the spectrometer is a wide wavelength range covering from 300 to 1100 nm. Furthermore, the wavelength resolution of the device reaches picometer level. In comparison with conventional spectrometers, the novel spectrometer has distinct advantages of small size, low cost, high resolution, wide spectral measurement range, real-time measurement, and so on.
Evanescent wave coupled spectroscopic sensing using Smartphone
Abstract: Present letter demonstrates a technique that utilizes the camera of a smartphone for evanescent wave coupled spectroscopic sensing. Using simple optical components, the camera of the smartphone is converted into a highly resolved spectrometer (0.305nm per pixel) and by using a right-angled glass prism the evanescent field of the internally reflected light signal from a broadband optical source is allowed to interact with the external medium. The primary advantages of the proposed sensing technique are its compactness, portability and cost-efficiency.
Imaging Spectroscopy and the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS)
Abstract: Imaging spectroscopy is of growing interest as a new approach to Earth remote sensing. The Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) was the first imaging sensor to measure the solar reflected spectrum from 400 nm to 2500 nm at 10 nm intervals. The calibration accuracy and signal-to-noise of AVIRIS remain unique. The AVIRIS system as well as the science research and applications have evolved significantly in recent years. The initial design and upgraded characteristics of the AVIRIS system are described in terms of the sensor, calibration, data system, and flight operation. This update on the characteristics of AVIRIS provides the context for the science research and applications that use AVIRIS data acquired in the past several years. Recent science research and applications are reviewed spanning investigations of atmospheric correction, ecology and vegetation, geology and soils, inland and coastal waters, the atmosphere, snow and ice hydrology, biomass burning, environmental hazards, satellite simulation and calibration, commercial applications, spectral algorithms, human infrastructure, as well as spectral modeling.
Application[edit | edit source]
Ethylene optical spectrometer for apple ripening monitoring in controlled atmosphere store-houses
Abstract: In today's store-houses the ripening of fruit is controlled by managing the ethylene concentration in the ambient atmosphere. Precise and continuous ethylene monitoring is very advantageous since low ethylene concentrations are produced by the fruit itself and are indicative of its ripeness, and on other occasions, ethylene is externally added when ripeness or degreening of the product must be promoted. In this work, a multichannel mid-infrared spectrometer for ethylene measurement is built and characterized. The instrument contains additional channels to reject potential cross-interferences like ammonia and ethanol. Additionally, these channels are useful for monitoring a potential malfunction of the cooling system and possible fouling of the fruit, respectively. The complete spectrometer contains a silicon-based macroporous infrared (IR) emitter, a miniaturized long path cell (white cell), a four-channel detector module, low-noise analog amplification and filtering, and a microcontroller-based lock-in amplifier. The new inner architecture of the detector module features a fourfold thermopile array with narrow band optical filters attached by flip-chip technology, and a Fresnel lens array attached on the lid of the package. Laboratory tests show that the system is able to distinguish between ammonia and ethylene, featuring a detection limit of 30 ppm and 160 ppm (95% confidence) for ethylene and ammonia, respectively. Field tests show that the spectrometer is suitable as an ethylene alarm to detect fruit ripening and prevent fruit to decline into senescence. Simulation results show that system selectivity could be improved by setting ammonia channel to another absorption wavelength.
Analysis of the repetitively pulsed dual‐beam thermo‐optical absorption spectrometer
Abstract: An analysis is presented for the repetitively pulsed dual‐beam thermo‐optical absorption spectrometer, which has been used recently to determine the absorption strengths of several organic liquids in the visible spectral region covered by the cw tunable dye laser. The model succeeds in describing the development of the thermal lens on a pulse‐by‐pulse basis. The equations derived are then used to optimize the spectrometer design with respect to the parameters which are under the control of the experimenter. It is further demonstrated how one identifies the region of linear operation of the spectrometer. Finally, it is shown how the relative absorptivities of compounds may be determined.
Frequency-domain multisource optical spectrometer and oximeter
Abstract: We have designed and constructed a near-infrared spectrometer for the non-invasive optical study of biological tissue. This instrument works in the frequency-domain and employs multiple source-detector distances to recover the absorption coefficient ((mu) (alpha )) and the reduced scattering coefficient ((mu) s') of tissue. The light sources are eight light emitting diodes (LEDs) whose intensities are modulated at a frequency of 120 MHz. Four LEDs emit light at a peak wavelength of 715 nm ((lambda) 1), while the other four LEDs emit at a peak wavelength of 850 nm ((lambda) 2). From the frequency-domain raw data of phase, dc intensity, and ac amplitude obtained from each one of the eight light sources, which are located at different distances from the detector fiber, we calculate (mu) (alpha ) and (mu) s' at the two wavelengths (lambda) 1 and (lambda) 2. The concentrations of oxy- and deoxy-hemoglobin, and hence hemoglobin saturation, are then derived from the known extinction coefficients of oxy- and deoxy-hemoglobin at (lambda) 1 and (lambda) 2. The statistical error in the measurement of the optical coefficients due to instrument noise is about 1 - 2%. The accuracy in the determination of the absolute value of the optical coefficients is within 10 - 20%. Preliminary results obtained in vivo on the forearm of a volunteer during an ischemia measurement protocol are presented.
Miniaturized spectrometer employing planar waveguides and grating couplers for chemical analysis
Abstract: Polymeric and metal oxide planar waveguides were used to demonstrate the potential of a miniature spectrometer. Multiwavelength light was transmitted through the substrate and coupled into the waveguide through a diffraction grating located at the substrate/waveguide interface. A second diffraction grating spatially dispersed the light propagated through the waveguide into component wavelengths for rapid analysis with a photodiode array detector. These results suggest that planar waveguides can be used to perform attenuated total internal reflection measurements in the visible and near-IR regions for chemical analysis of weak vibrational overtones and combination modes with effective path lengths of several millimeters.
White-light spectral interferometric technique to measure the wavelength dependence of the spectral bqandpass of a fibre-optic spectrometer
Abstract: A spectral-domain white-light interferometric technique with channelled spectrum detection is used to measure the wavelength dependence of the spectral bandpass of a fibre-optic spectrometer. In an experimental setup comprising a halogen lamp, a non-dispersive Michelson interferometer and the spectrometer to be measured, spectral interferograms are recorded for different optical path differences (OPDs) between interfering beams. By processing the recorded spectral interferograms using discrete filtering and a fringe amplitude demodulation method, spectral fringe visibilities, first, as a function of the wavelength for given OPDs, and second, as a function of the OPD at given wavelengths, are obtained. It is confirmed, in accordance with theory, that the latter spectral fringe visibility functions are Gaussian functions with maxima and widths dependent on the wavelength. From the widths of the Gaussian spectral fringe visibility functions the wavelength dependence of the spectrometer bandpass is determined over a wide spectral range.
A simple miniature optical spectrometer with a planar waveguide grating coupler in combination with a plano-convex lens Kalyani Chaganti, Ildar Salakhutdinov, Ivan Avrutsky, Gregory W. Auner
Abstract: A miniature optical spectrometer with a thin-film planar waveguide grating coupler in combination with a miniature plano-convex focusing lens has been investigated. With optical part of the spectrometer as small as 0.2 cubic cm, the spectral resolution varies from 0.3 nm to 4.6 nm within the wavelength range 488.0 nm – 632.8 nm. Follow up to "Concept of a Miniature Optical Spectrometer Using Integrated Optical and Micro-Optical Components.”
[Automatic wavelength calibration procedure for use with an optical spectrometer and array detector http://pubs.rsc.org/en/content/articlelanding/1995/ja/ja9951000253/unauth#!divAbstract]
Abstract: Échelle spectrometers with cross-dispersion are often used in emission spectroscopy owing to their high spectral resolution and good light throughput. The resultant two-dimensional dispersion plane is ideally suited to array detectors such as the charge-injection device (CID) or charge-coupled device (CCD). The successful coupling of an échelle spectrometer with an array detector permits true simultaneous spectroscopy to be performed over a large spectral range. In order to correctly identify spectral features it is necessary to have an accurate wavelength calibration function which maps the CCD/CID pixel co-ordinates to wavelength. A new approach to the wavelength calibration of optical spectrometers with array detection is proposed that does not involve a direct modelling of the spectrometer dispersion. Instead, the difference between an ideal conceptual spectrometer and the physical instrument is modelled. The procedure is able to compensate for the effects of manufacturing tolerances and local temperature and pressure conditions. Preliminary results, obtained by simulation with a computer-modelled échelle spectrometer, has shown that a sub-pixel accuracy in the predicted position of spectral lines can be achieved over a temperature range 5–35 °C. NOTE: Pending inter-library Loan.
Study on Predicting Total Acid Content and Soluble Sugar of Tomato Juice by Near Infrared Optical Fiber Spectrometer Technique
Abstract: In order to explore a simple, rapid and efficient tomato quality detection method, in the present experiment near infrared spectroscopy and optical fiber sensing technology were applied to quickly measure the nutrition ingredient content in tomato juice samples. The main instrument used in this experiment was near infrared optical fiber spectrometer in a wavelength range from 900 to 2 500 nm, which measured the absorbance of the tomato juice samples; A collection of one hundred and sixty-four tomato juice samples were selected as the standard samples, the spectra and the corresponding chemical value were measured. Partial least squares (PLS) was adopted to establish the mathematical model of the total acid and soluble sugar content in tomato juice samples, and the regression equation was statistically analysed. The total acid in tomato juice prediction correlation coefficient was 0.967, calibration standard deviation (RMSEC) was 0.133, standard error of prediction (RMSEP) was 0.103; the soluble sugar prediction correlation coefficient is 0.976, calibration standard deviation (RMSEC) was 0.463, and the standard error of prediction (RMSEP) was 0.460. The above data achieved better forecasting results, which showed that the method of quantitative analysis of tomato fruit multicomponent content was feasible. The method is rapid, simple and can do multicomponent analysis on the same sample simultaneously. It is a promising sensor and gradually becoming a international research focus in sensor field.
Assessment of solar electricity potentials in North Africa based on satellite data and a geographic information system
Abstract: Solar thermal power plants will provide a major share of the renewable energy sources needed in the future. STEPS, an evaluation system for solar thermal power stations, was designed to calculate the performance of such power stations as a function of direct solar radiation, geographical conditions (land slope, land cover, distance from cooling water resources, etc.), infrastructure (pipelines, electricity grids, streets etc.) and the configuration and performance of a selected solar thermal power plant concept. A cloud index derived from METEOSAT satellite images is used to calculate the direct solar radiation resource. A geographic information system (GIS) is used to process all the parameters for site assessment. In order to demonstrate the concept, an analysis of Northern Africa was performed with STEPS providing a ranking of sites with respect to the potential and cost of solar thermal electricity for a particular power plant configuration. Results were obtained with high spatial and temporal resolution.
The Keck Low-Resolution Imaging Spectrometer Oke, J. B., Cohen, J. G., Carr, M., Cromer, J., Dingizian, A., Harris, F. H., ,
Abstract: This article covers the design and implementation of a simple low resoltion imaging spectrometer. This was used in the Keck telecsope Mauna Kea, Hawaii.
[http://mas.arc.nasa.gov/reference/MAS.pdfAirborne Scanning Spectrometer for Remote Sensing of Cloud, Aerosol, Water Vapor, and Surface Properties]
An airborne scanning spectrometer was developed for measuring reflected solar and emitted thermal radiation in 50 narrowband channels between 0.55 and 14.2 m m. The instrument provides multispectral images of outgoing radiation for purposes of developing and validating algorithms for the remote sensing of cloud, aerosol, water vapor, and surface properties from space. The spectrometer scans a swath width of 37 km, perpendicular to the aircraft flight track, with a 2.5-mrad instantaneous field of view. Images are thereby produced with a spatial resolution of 50 m at nadir from a nominal aircraft altitude of 20 km. Nineteen of the spectral bands correspond closely to comparable bands on the Moderate Resolution Imaging Spectroradiometer ( MODIS ) , a facility in- strument being developed for the Earth Observing System to be launched in the late 1990s. This paper describes the optical, mechanical, electrical, and data acquisition system design of the MODIS Airborne Simulator and presents some early results obtained from measurements acquired aboard the National Aeronautics and Space Administration ER-2 aircraft that illustrate the performance and quality of the data produced by this instrument
The quantum dot spectrometer J. L. Jimenez, L. R. C. Fonseca, D. J. Brady, and J. P. LeburtonD. E. Wohlert and K. Y. Cheng
Abstract:We propose a novel photodetector capable of multi-spectral channel operation. The device makes use of the ability of a quantum dot plane to capture an optical spectrum, and of a resonant-tunneling structure to perform spectrally sensitive read-out. We present a design made out in the InAs–GaAs–Al x Ga 1 2 x As system. We also present realistic simulations of the optical channel capabilities, as well as a discussion of the possible problems of the device.
See also[edit | edit source]