INSPEX: Optimize Range Sensors for Environment Perception as a Portable System.

Environment perception is crucial for the safe navigation of vehicles and robots to detect obstacles in their surroundings. It is also of paramount interest for navigation of human beings in reduced visibility conditions. Obstacle avoidance systems typically combine multiple sensing technologies (i.e., LiDAR, radar, ultrasound and visual) to detect various types of obstacles under different lighting and weather conditions, with the drawbacks of a given technology being offset by others. These systems require powerful computational capability to fuse the mass of data, which limits their use to high-end vehicles and robots. INSPEX delivers a low-power, small-size and lightweight environment perception system that is compatible with portable and/or wearable applications. This requires miniaturizing and optimizing existing range sensors of different technologies to meet the user's requirements in terms of obstacle detection capabilities. These sensors consist of a LiDAR, a time-of-flight sensor, an ultrasound and an ultra-wideband radar with measurement ranges respectively of 10 m, 4 m, 2 m and 10 m. Integration of a data fusion technique is also required to build a model of the user's surroundings and provide feedback about the localization of harmful obstacles. As primary demonstrator, the INSPEX device will be fixed on a white cane.

Novel Applications of Laser-Induced Breakdown Spectroscopy.

The goal of this review article is to provide a description of recent and novel laser-induced breakdown spectroscopy (LIBS) applications and developments, especially those discussed during the NASLIBS Conference, held during SciX in Providence, RI, in September 2015. This topic was selected in view of the numerous recent overall review papers that have successfully given a broad view of the current understanding of laser-material interactions and plasma development and have also discussed the wide landscape of analytical applications of LIBS. This paper is divided into sections that focus on a few of the many applications under development in the LIBS community. We provide a summary of updates to calibration-free LIBS (CF-LIBS) and associated developments using plasma characteristics to improve quantification in LIBS output, both in a dedicated section and as applications are discussed. We have also described the most recent publications studying the sources, generation, and use of molecular features in LIBS, including those naturally present in the spectra of organic materials, and those induced with the addition of salts to enable the measurement of halogens, not typically present in LIBS signals. In terms of development of applications of LIBS, we focused on the use of LIBS for indirect measurements such as pH and degree of humification in soil and heating value in coal. We also reviewed the extant literature on LIBS analysis of agricultural materials, coal, minerals, and metals. Finally, we discuss the nascent developments of spatially heterodyne spectroscopy, a method that seeks to circumnavigate a serious drawback of most spectrometers - very small optical throughput - through the use of interferometers.

Laser-induced breakdown spectroscopy of steel: a comparison of univariate and multivariate calibration methods.

Laser-induced breakdown spectroscopy (LIBS) was carried out on twenty-three low to high alloy steel samples to quantify their concentrations of chromium, nickel, and manganese. LIBS spectral data were correlated to known concentrations of the samples and three calibration methods were compared. A standard LIBS calibration technique using peak area integration normalized by an internal standard was compared to peak area integration normalized by total light and the multivariate statistical technique of partial least squares. For the partial least squares analysis, the PLS-1 algorithm was used, where a predictive model is generated for each element separately. Partial least squares regression coefficients show that the algorithm correctly identifies the atomic emission peaks of interest for each of the elements. Predictive capabilities of each calibration approach were quantified by calculating the standard and relative errors of prediction. The performance of partial least squares is on par with using iron as an internal standard but has the key advantage that it can be applied to samples where the concentrations of all elements are unknown.

Fiber-optic spark delivery for gas-phase laser-induced breakdown spectroscopy.

This article reports what are to the authors' knowledge the first gas-phase laser-induced breakdown spectroscopy (LIBS) measurements using a fiber-optically delivered spark. A silver- and polymer-coated hollow fiber delivered high-energy nanosecond 1064 nm Nd:YAG laser pulses, which were focused to generate high-energy-density plasmas in ultra-lean methane-air mixtures. Emissions from these plasmas were collected and spectroscopically analyzed to quantify relative fuel-to-air ratio. These measurements were compared with others made using traditional LIBS techniques without the fiber-optically delivered spark. Similar results were obtained, but with larger shot-to-shot variability, for the case of the fiber-optically delivered spark.

Single diode laser sensor for wide-range H2O temperature measurements.

A single diode laser absorption sensor (near 1477 nm) useful for simultaneous temperature and H2O concentration measurements is developed. The diode laser tunes approximately 1.2 cm(-1) over three H2O absorption transitions in each measurement. The line strengths of the transitions are measured over a temperature range from 468 to 977 K, based on high-resolution absorption measurements in a heated static cell. The results indicate that the selected transitions are suitable for sensitive temperature measurements in atmospheric pressure combustion systems using absorption line ratios. Comparing the results with HITRAN 96 data, it appears that these transitions will be sensitive over a wide range of temperatures (450-2000 K), suggesting applicability for combustion measurements.

Laser-induced breakdown spectroscopy detection and classification of biological aerosols.

Laser-induced breakdown spectroscopy (LIBS) is examined as a potential method for detecting airborne biological agents. A spectrally broadband LIBS system was used for laboratory measurements on some common biological agent simulants. These measurements were compared to those of common, naturally occurring biological aerosol components (pollen and fungal spores) to determine the potential of LIBS for discriminating biological agents from natural background aerosols. A principal components analysis illustrates that linear combinations of the detected atomic lines, which are present in different ratios in each of the samples tested, can be used to discriminate biological agent simulants from other biological matter. A more sensitive, narrowband LIBS instrument was used to demonstrate the detection of single simulant (Bg) particles in the size range 1-5 microns. Ca, Mg, and Na, which are present in varying concentrations between 0.3 and 11% (by mass) in the Bg particles, were observed in single particles using LIBS.

Laser-induced breakdown spectroscopy for on-line engine equivalence ratio measurements.

Laser-induced breakdown spectroscopy (LIBS) has been used to measure the equivalence ratio of a spark-ignited engine in a laboratory setting. Spectral features of C (711.3 nm), O (776.6 nm), N (746.3 and 743.8 nm), and CN (broad emission 707-734 nm) were used to quantify the equivalence ratio over a range from phi = 0.8 to phi = 1.2. The C/N and C/O peak ratios were found to be successful measurement metrics, compared with a standard exhaust gas oxygen analyzer, for averaged measurements. Some variation in the measurements was observed as a function of engine load. Single-shot data based on a CN/air peak ratio were evaluated using a separate calibration from averaged measurements, and the average of the single-shot data was found to agree well with the exhaust gas oxygen analyzer. The scatter in the single-shot data was substantially higher at lower equivalence ratios. The measurements including the CN peak were slightly sensitive to load, possibly due to pressure changes in the sample as the load increases, or possibly due to changes in the particle size distribution in the gas stream.