Microwave Radiometric Detection of Oil SlicksRadiometry and the Detection of Optical RadiationOptical Systems Design Detection EssentialsOptoelectronic Workshops 7: Advanced Technology for Radiometry and the Detection of Optical RadiationStudies of Radio Frequency Interference Detection Methods in Microwave RadiometryPassive Infrared DetectionAdvances in Radiometry ResearchDetection and Assessment of Dental CariesMicrowave and Millimeterwave Remote Sensing for Security ApplicationsNon-Imaging Microwave and Millimetre-Wave Sensors for Concealed Object DetectionIntroduction to Radiometry and Photometry, Second EditionOptical Radiation Measurements: Grum, F. C., Becherer, R. RadiometryMicrowave Radiometric Studies in Relation to Mine DetectionMicrowave Radiometry and Remote Sensing of the Earth's Surface and AtmosphereMILLIMETER WAVE RADIOMETRIC DETECTION OF TARGETS OBSCURED BY FOLIAGE.Applied Photometry, Radiometry, and Measurements of Optical LossesPassive Standoff Detection of Chemical Vapors by Differential FTIR RadiometryClinical Application of Microwave Radiometry Techniques in the Detection of CancerPhotometry, Radiometry, and Measurements of Optical LossesRadiometryIce/frost Detection Using Millimeter Wave RadiometryFeasibility Study of Radiometry for Airborne Detection of Aviation HazardsEM Detection of Concealed TargetsLaser Photothermal Radiometry for the Detection of Early Enamel DemineralizationRadio Frequency Radiometry for the Remote Airborne Detection of Small Forest FirDetection and Characterization of Nuclear CloudsAn Application of Pattern Recognition to Radiometric Target DetectionTheory of Broadband Autocorrrelation Radiometry for Spectral Line DetectionInfrared Detectors and SystemsRadiometry Detection of Acoustic SignalsDetection of Greenbug Infestation Using Ground-based RadiometryRadiometry and the Detection of Optical RadiationW-band Radiometry for the Non-invasive Investigation of MaterialsHuman Presence Detection Using Millimeter-wave RadiometryRadiometry for Low Target DetectionUse of Airborne Microwave Radiometry for the Detection and Investigation of Oil Slicks at SeaFeasibility Study of Radiometry for Airborne Detection of Aviation HazardsIntroduction to Radiometry and PhotometryRadio Frequency Interference Characterization and Detection in L-band Microwave RadiometryDetection of Abandoned Underground Coal Mines by Geophysical Methods

Radiometry and the Detection of Optical Radiation

This paper presents a new low-noise high-accuracy laser range finder based on the Time-Of- Flight (TOF) method. A Q-switched Nd:YAG laser at 1064 nm as a source and a SLIK avalanche photodiode as a detector are used. The optical section of the system including ZnS/MgF2 optical filter, designed by C ++ and Zemax software, has been successfully implemented and tested. The quality factor of the optical filter is obtained about 2.53. Using the 1.5 MW Nd:YAG laser, the lowest detectable optical power is limited to about 8.14 nW. The absolute range finding error in the range of 0.3-20 km is also measured asr= ± 50 cm. Furthermore, the sampling rate of the distance measurement can be adjusted between 1 and 20 samples per second.

/pdf/low-noise-high-accuracy-tof-laser-range-finder-1pb0qc0qe7.pdf

Low-Noise High-Accuracy TOF Laser Range Finder

This dissertation reports on the synthesis, structural and thermal characterization and electrical and thermal transport properties of a variety of strongly correlated spinels. General structure property relationships for electrical and thermal transport are discussed. However, the relationship between thermopower and features of the crystal structure such as spin, crystal field, anti-site disorder, and structural distortions are explored in depth. The experimental findings are reported in the context of improving existing oxide thermoelectric materials, screening for new materials or using thermopower as a unique characterization tool to determine the cation distribution in spinels. The need for improved n-type oxide thermoelectric materials has led researchers to consider mixed valence (+3/+4) manganese oxides. Contrary to previous findings we report herein that the LiMn2O4 compound reaches the relatively large n-type thermopower of -73 μV/K which is three times larger than the value observed in other

Oxide Thermoelectrics: The Role of Crystal Structure on Thermopower in Strongly Correlated Spinels

Measurement of atmospheric water vapor is very important for understanding the Earth''s climate and water cycle. The remote sensing Differential Absorption Lidar (DIAL) technique is a powerful method to perform such measurement from aircraft and space. This thesis describes a new advanced detection system, which incorporates major improvements regarding sensitivity and size. These improvements include a low noise advanced avalanche photodiode detector, a custom analog circuit, a 14-bit digitizer, a microcontroller for on board averaging and finally a fast computer interface. This thesis describes the design and validation of this new water vapor DIAL detection system which was integrated onto a small Printed Circuit Board (PCB) with minimal weight and power consumption. Comparing its measurements to an existing DIAL system for aerosol and water vapor profiling validated the detection system.

/pdf/advanced-atmospheric-water-vapor-dial-detection-system-1qwbl7hi9n.pdf

Advanced Atmospheric Water Vapor DIAL Detection System

In this paper, we present a high accuracy laser range finder and velocimeter using ultra-fast time-to-digital converter (TDC). The system operation is based on the measuring the round-trip time of a narrow laser pulse. A low-dark current high-speed PIN photodiode is used to detect the triggered laser beam and to produce start signal. The pulsed laser diode generates 45W optical power at 30ns duration time and 905nm wavelength. A high-responsivity avalanche photodiode (APD) detects the reflected beam from the target. An optical head including beam splitter, lenses and optical filters is also designed and implemented. The signal conditioner of the system includes pre- and post-amplifiers, comparator, opto-isolators and monostable. By using a 3MV/W reach-through structure avalanche photodiode and a wideband pre-amplifier, the pre-amplifier output reaches 15.9mV, resulting from the minimum detectable optical power. The APD temperature and as a result its responsivity is controlled by a thermoelectric controller unit. The start and stop signals from PIN and APD are led to the time-to-digital converter to count the round- trip time of the laser beam. The system is tested by a retro-reflector as a target for 30- 1200m distances. The resolutions of the distance and velocity measurement are limited to 18.75mm and 1.2m/s, respectively. In the worst condition, the minimum reflected optical power is limited to about 5.3nW in 1.2km distance.

/pdf/unified-pulsed-laser-range-finder-and-velocimeter-using-5698qmx7gu.pdf

Unified pulsed laser range finder and velocimeter using ultra-fast time-to-digital converter

Avalanche photodiode (APDs) are quantum optical detectors that are used for visible and near infrared optical detection applications. Although APDs are compact, rugged, and have an internal gain mechanism that is suitable for low light intensity; their responsivity, and therefore their output, is strongly dependent on the device temperature. Thermoelectric coolers (TEC) offers a suitable solution to this problem. A TEC is a solid state cooling device, which can be controlled by changing its current. TECs are compact and rugged, and they can precisely control the temperature to within 0.1 degrees C with more than a 150 degree C temperatue gradient between its surfaces. In this memorandum, a proportional integral (PI) temperature controller for APDs using a TEC is discussed. The controller is compact and can successfully cool the APD to almost 0 degrees C in an ambient temperature environment of up to 27 percent C.

/pdf/temperature-control-of-avalanche-photodiode-using-3ssjf68539.pdf

Temperature Control of Avalanche Photodiode Using Thermoelectric Cooler

For lidar measurements of ozone, photomultiplier tube (PMT) detector signal-induced noise represents a fundamental problem that complicates the extraction of information from lidar data. A new method is developed to significantly reduce signal-induced noise in lidar receiver PMT detectors. The electron optics of the lidar photomultiplier detector is modified to filter the source of signal-induced noise. A mesh electrode external to the PMT is utilized to control photoemission and disorient electron trajectories from the photocathode to the first dynode. Experiments were taken both with simulated and actual lidar return signals at Langley Research Center. Results show at least 40 percent more accurate ozone number density values with a mesh voltage of 60 V applied than with no voltage applied.

https://ntrs.nasa.gov/api/citations/20000013443/downloads/20000013443.pdf

Young Russell J. De

Papers

Temperature Control of Avalanche Photodiode Using Thermoelectric Cooler

A New Method for Reduction of Photomultiplier Signal-Induced Noise