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From page 154... ... 4 Active Electro-Optical Component Technologies As has been described in Chapters 2 and 3, current and emerging active electro-optical (EO) sensing systems are implemented in many different modalities. Read the entire page →
From page 155... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 155 employ either diode or solid-state lasers, with the latter often combined with nonlinear optics. This looks to be the case for the foreseeable future, owing to a favorable combination of output format, operating wavelength, relatively high efficiency, ruggedness, compact size, and reliability. Read the entire page →
From page 156... ... 156 LASER RADAR FIGURE 4-1 Reprinted with permission from The Photonics Handbook, online at http://www.PhotonicsHandbook.com. Copyright 2013. Read the entire page →
From page 157... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 157 small emitting region. To effectively capture all of the power from the diode laser requires fast optics, at least for the fast-axis light, and this is accomplished with specialized aspheric optics, often fastened directly to the diode-laser package. Read the entire page →
From page 158... ... 158 LASER RADAR FIGURE 4-2 Diagram of "bar" lasers. SOURCE: © Jeniptik Laser GmbH. Read the entire page →
From page 159... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 159 FIGURE 4-3 Several different VCSEL structures. SOURCE: Courtesy of Princeton Optronics, Inc. Read the entire page →
From page 160... ... 160 LASER RADAR layers, typically 10-15 in number. Devices based on other material combinations have been demonstrated but show inferior performance. Read the entire page →
From page 161... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 161 Interband Cascade Lasers A related semiconductor laser that has features of both interband and cascade diode lasers is the aptly named interband cascade laser (ICL) Read the entire page →
From page 162... ... 162 LASER RADAR difference for light being absorbed (upward transition) and that being emitted (downward transition) Read the entire page →
From page 163... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 163 A simple electronic system with just two energy levels and no lattice displacement (Figure 4-5 left) cannot be used to make a laser, since the material becomes transparent when a population inversion occurs. Read the entire page →
From page 164... ... 164 LASER RADAR FIGURE 4-6 Simplified energy-level diagram for an Nd3+ ion. SOURCE: Courtesy of Rani Arieli, Weizmann Institute of Science. Read the entire page →
From page 165... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 165 FIGURE 4-7 Absorption and emission spectra for Ti:sapphire. SOURCE: Courtesy of Peter Moulton, Q-Peak, Inc., http://www.qpeak.com/. Read the entire page →
From page 166... ... 166 LASER RADAR FIGURE 4-8 Schematic diagram of first ruby laser. SOURCE: Lawrence Livermore National Security, LLC and the Department of Energy. Read the entire page →
From page 167... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 167 1. Availability in a size suited for the pumping, lasing configuration; low optical loss at the pump and laser wavelengths; ability to support active-ion doping levels high enough to absorb the pump light in the desired volume. Read the entire page →
From page 168... ... 168 LASER RADAR • Al 2 O 3 (sapphire) Read the entire page →
From page 169... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 169 approximation, as a lens. The lens is positive for the majority of materials, which exhibit a positive change in the refractive index with temperature. Read the entire page →
From page 170... ... 170 LASER RADAR absorption. (This arrangement would not be possible with lamp pumping.) Read the entire page →
From page 171... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 171 FIGURE 4-9 Schematic of diode end-pumped solid-state laser. Lamp-pumped Nd:YAG lasers convert 2-3 percent of the lamp energy into laser output, with much of the lamp output not absorbed by the laser material. Read the entire page →
From page 172... ... 172 LASER RADAR • Diodes can be powered by low-voltage power supplies or batteries, in contrast to the highvoltages needed to drive lamps. • With improvements in diode fabrication, laser operating times before pump replacement are typically three orders of magnitude longer than with lamps. Read the entire page →
From page 173... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 173 FIGURE 4-11 Schematic of diode side-pumped laser. So-called side- or transverse-pumped designs with diodes can be employed to generate higher powers (and energies in the pulsed mode, see below) Read the entire page →
From page 174... ... 174 LASER RADAR FIGURE 4-12 High-brightness, high-power stacked bars. SOURCE: Courtesy of DILAS. Read the entire page →
From page 175... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 175 FIGURE 4-13 Left: Diagram of end-pumped slab design used for Vesta gain module. Right: Photograph of the gain module. Read the entire page →
From page 176... ... 176 LASER RADAR problem is worsened by the relatively small cross sections for the Er transitions, for both absorption and emission. One solution to the problem is to add Yb3+ ions into the crystal. Read the entire page →
From page 177... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 177 The ability to store large amounts of energy in the laser medium is one of the key advantages of bulk solid-state lasers and is unique to them. (As noted below, fiber-format lasers, although capable of high CW power levels, have major challenges in storing energy.) Read the entire page →
From page 178... ... 178 LASER RADAR nonradiative processes. In addition, for the same lifetime, the gain cross section is inversely proportional to the spectral linewidth of the gain. Read the entire page →
From page 179... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 179 terms of wavelength is larger than for Ti:sapphire, in terms of frequency it is less, and the latter actually determines the shortest pulsewidth for mode-locked operation, as discussed below. Many moderate-energy solid-state lasers (for example, those based on Nd:YAG) Read the entire page →
From page 180... ... 180 LASER RADAR FIGURE 4-14 Interferometric autocorrelation signal from mode-locked Ti:sapphire laser showing data and fit to 6.5 ns pulse. Read the entire page →
From page 181... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 181 Although Ti:sapphire has been the standard source for generation and amplification of fs-duration pulses, there are many applications that benefit from pulses with central wavelengths longer than 800 nm or simpler laser systems. With bulk crystals, systems employing Yb- or Ho-doped media can provide pulses with durations in the 50- to 200-fs range, and CPA techniques can be employed for amplification. Read the entire page →
From page 182... ... 182 LASER RADAR FIGURE 4-15 Schematic of pumped double-clad fiber laser. SOURCE: By Fl.png: Danielsoh8 derivative work: Das steinerne Herz (Fl.png) Read the entire page →
From page 183... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 183 this process may start with only tens of watts of power. SBS has a very limited gain linewidth, on the order of tens of magahertz, and can be circumvented by operating the fiber laser with a large spread of operating frequencies or adding frequency modulation onto a single-frequency input. Read the entire page →
From page 184... ... 184 LASER RADAR 1.3-m-long rod stage. 15 For short-pulse operation, the same sort of large-mode PC fiber was employed with a CPA configuration to produce 500 fs, 2.2 mJ pulses at a 5 kHz rate. Read the entire page →
From page 185... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 185 relaxation or for operation at longer wavelengths than possible from silica. Powers from the soft-glass fibers have tended not to exceed 100 W or so. Read the entire page →
From page 186... ... 186 LASER RADAR the fibers. At this point, none of the beam combining techniques has moved out of the basic developmental level to applications, and would present an expensive approach for active sensors. Read the entire page →
From page 187... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 187 only over very short lengths of material. Two important nonlinear processes are discussed next, both of which depend on second-order nonlinear effects in crystals. Read the entire page →
From page 188... ... 188 LASER RADAR creation of trapped electrons, an internal electric field, and a change in refractive index from this field that destroys the phase-matching condition. The second-order term that allows generation of a harmonic can be viewed as the combination of two wavelengths (of the fundamental light) Read the entire page →
From page 189... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 189 TABLE 4-1 Common Birefringent Crystals Used for Harmonic and Related Generation. Figure of merit Transparency Crystal (Acronym) Read the entire page →
From page 190... ... 190 LASER RADAR pattern of nonlinear-coefficient signs. 25 Such crystals are called periodically poled (PP) Read the entire page →
From page 191... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 191 high enough and the interaction length long enough, the gain in the OPA may be high enough to allow significant signal or idler power to build up from noise, and the device is referred to as an optical parametric generator (OPG) Read the entire page →
From page 192... ... 192 LASER RADAR average-power scaling to 33 W (330 mJ at 100 Hz) , 29 which held the record for a time as the highestaverage-power OPO. Read the entire page →
From page 193... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 193 Ho:YAG laser. In addition, the materials can be readily pumped by the relatively low peak powers available from pulsed fiber lasers. Read the entire page →
From page 194... ... 194 LASER RADAR FIGURE 4-16 Intensity as a function of wavelength for SC source based on a zirconium barium lanthanum aluminum sodium fluoride (ZBLAN) fiber driven by a Tm:fiber-based source, for different pump pulse formats. Read the entire page →
From page 195... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 195 Conclusion 4-2: Solid-state lasers seem favorable for active EO due to their combination of output format, operating wavelength, relatively high efficiency, ruggedness, compact size, and reliability. They can be considered coherency converters of their laser diode pump lasers. Read the entire page →
From page 196... ... 196 LASER RADAR "The APD is the solid-state equivalent of the photomultiplier tube in that both create many electrons from each incident photon. The number of electrons created per absorbed photon is the internal detector gain. Read the entire page →
From page 197... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 197 FIGURE 4-17 Excess noise factor plot for commonly used semiconductors for APDs. Read the entire page →
From page 198... ... 198 LASER RADAR The tunable bandgap semiconductor Hg 1-x Cd x Te is the only commonly used semiconductor that exhibits k = 0 behavior and therefore the electron initiated avalanche multiplication exhibits close to ideal APD characteristic of excess noise factor F(M) Read the entire page →
From page 199... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 199 FIGURE 4-18 Family of HgCdTe APD detectors in a variety of formats. Read the entire page →
From page 200... ... 200 LASER RADAR Geiger-Mode APDs Geiger-mode avalanche photodiode detectors (GM-APDs) are biased at voltages several volts above the breakdown voltage, typically much higher than biases of linear-mode detectors. Read the entire page →
From page 201... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 201 reset after photon detection because of a holdoff time, also called the dead time, during which the detectors are blinded. This issue can be mitigated by spreading the signal over multiple pixels to reduce the probability of a photon striking a blinded pixel. Read the entire page →
From page 202... ... 202 LASER RADAR FIGURE 4-20 Geiger-mode sensing concept. SOURCE: Melissa Choi, MIT-LL. Read the entire page →
From page 203... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 203 InGaAs-based APDs Linear-mode InGaAs APDs are commercially available in a variety of formats ranging from single pixel to 128 × 128 FPAs. As discussed above, due to the high k value of 0.4 the usable gain of conventional InGaAs is limited to ~10. Read the entire page →
From page 204... ... 204 LASER RADAR FIGURE 4-22 A 32 × 32 element InGaAs SCM-APD shown mounted with drive electronics. SOURCE: http://voxtel-inc.com/products/. Read the entire page →
From page 205... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 205 FIGURE 4-23 Broad spectral response from visible to MWIR is characteristic of front-side illuminated HDVIP e-APD. SOURCE: DRS Technologies, Dallas Texas. Read the entire page →
From page 206... ... 206 LASER RADAR FIGURE 4-25 Effect of noiseless gain. Left: APD gain vs. Read the entire page →
From page 207... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 207 FIGURE 4-26 Analog output showing single photon initiated events captured with a 4,330 nm cutoff HgCdTe detector at 84 K Read the entire page →
From page 208... ... 208 LASER RADAR TABLE 4-2 Performance Parameters of Various Linear-mode APD Photon Detectors Device Parameter Si Arpad HgCdTeb HgCdTec,d InGaAsa InAlAse QE (percent) Read the entire page →
From page 209... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 209 • For fast-moving targets or when the measuring time or the measuring number of pulses is limited, LM-APD may have an advantage over GM-APD, depending on the speed of the target. • Intensity measurements in LM-APDs can be performed with fewer pulses than in GM-APDs. Read the entire page →
From page 210... ... 210 LASER RADAR TABLE 4-3 Performance Parameters Comparison of Linear Geiger and Coherent Mode Detectors Parameter Linear Geiger Coherent 4 4 Dark count rate Critical target <10 Critical target <10 Not critical I dark overcome by LO Spectral range NIR – LWIR NIR – SWIR NIR – LWIR (Linear) Bandwidth GHz GHz GHz Multipulse resolution on a Nanoseconds Microseconds Nanoseconds single pixel Dead time from after pulsing Intensity Yes (single pulse) Read the entire page →
From page 211... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 211 • Jitter < 100 ps. • 1024 × 768, 20 µm pitch gated mode ROIC, 256 × 256 w/ 300 kV/A 100 MHz flash ROIC • Pros – HgCdTe excess noise factor ~1. Read the entire page →
From page 212... ... 212 LASER RADAR FRAMING CAMERAS Framing cameras are used for digital holography and polarization-based flash 3-D ladar. These are conventional passive FPAs, built with gated imaging capability in the ROIC. Read the entire page →
From page 213... ... ACTIVE ELECTRO-OPT EL TICAL COMPO ONENT TECH HNOLOGIES 213 FIGURE 4-28 MWIR (le and SWIR (right) imager taken with a 640 × 480, 12 µm pixel cam operating at 150 4 eft) Read the entire page →
From page 214... ... 214 LASER RADAR FIGURE 4-29 Illustration of the principle of range-gated imaging applied to a target in the midst of large background clutter. The use of 1.57 µm laser can significantly reduce the haze common in the marine environment. Read the entire page →
From page 215... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 215 speckle as is common due to interference effects. The image processed region within the green square drastically reduces the speckle effects, improving the image quality relative to the region outside the square. Read the entire page →
From page 216... ... 216 LASER RADAR Conclusion 4-8: In the next few years it is expected both Geiger and linear-mode avalanche photodiode technologies will continue to develop to similar array sizes with comparable sensitivity. As the formats grow the pixel pitch will need to shrink to keep the size of the collection optics practical and from growing unreasonably large. Read the entire page →
From page 217... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 217 FIGURE 4-31 RULLI detector elements and concept. Read the entire page →
From page 218... ... 218 LASER RADAR FIGURE 4-33 Spectral dependence of the quantum efficiency for several available photocathode materials. Read the entire page →
From page 219... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 219 Because the scene, whether in passive imaging or ladar mode, is built up one photon at a time with a maximum count rate of 1-2 MHz, the imaging time for a scene can be rather long. RULLI/NCam employs both position and attitude knowledge as well as motion compensation and registration algorithms to build the scene images as well as identify movers within a scene. Read the entire page →
From page 220... ... 220 LASER RADAR FIGURE 4-36 Graphene's honeycomb lattice of carbon atoms. SOURCE: By AlexanderAlUS (Own work) Read the entire page →
From page 221... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 221 FIGURE 4-37 For a single layer of graphene the Fermi energy E F changes with gate voltage V g ; positive V g induce electrons and negative V g induce holes. The carrier concentrations is n = αV g , where the coefficient α ≈ 7.2 × 1010/cm2/V for field-effect devices with a 300 nm SiO 2 layer used as a dielectric. Read the entire page →
From page 222... ... 222 LASER RADAR Not all graphene properties are optimal. The band structure yields a constant value for the conductance and optical absorption over a wide spectral range, from visible to infrared.108,109 The resultant probability of a photon absorption in a single layer of graphene is about 2.3 percent.112,110 For high quantum efficiency detectors, multiple layers of graphene are needed. Read the entire page →
From page 223... ... ACTIVE ELECTRO-OPT EL TICAL COMPO ONENT TECH HNOLOGIES 223 FIGUURE 4-38 The schematic vie of the A-G e ews GNR-based IR p photodetector with electrically ind duced PIN junction. Read the entire page →
From page 224... ... 224 LASER RADAR FIGURE 4-39 Fabrication of broadband graphene experimental detector: (a) a monolayer of graphene is placed on a SiO 2 /Si substrate, (b) Read the entire page →
From page 225... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 225 The slow response is attributed to traps, and there are multiple ways to reduce trap times and densities. It is well know that the boundary edges of graphene can change its character from semiconductor to metallic and even introduce defects. Read the entire page →
From page 226... ... 226 LASER RADAR detector performance by use of small 3-D embedded nanoparticles called quantum dots. 123 The electronic structure of a QD is modified compared with bulk materials due the relatively large surface boundaries and low volume, and the consequently confined size of electronic excitations, called excitons, within the dot. Read the entire page →
From page 227... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 227 FIGURE 4-41 (a) Laboratory apparatus, (b) Read the entire page →
From page 228... ... 228 LASER RADAR Research Directions The lack of theoretical performance from QDIPs could be related to QD growth mechanisms. The standard QD material is grown by MBE and materials such as InAs/GaAs. Read the entire page →
From page 229... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 229 FIGURE 4-43 An example of optical antennas that enhance optical electric fields to a localized area for enhanced detection capability. Such tiny structures can be combined into sparse detector arrays. Read the entire page →
From page 230... ... 230 LASER RADAR 18-foldenhancement of electric field intensity near the partial gold shell on the nanopillar sidewalls. A pitch of 580 nm gave resonances within the absorption spectrum of the In 0.35 Ga 0.65 As material. Read the entire page →
From page 231... ... ACTIVE ELECTRO-OPT EL TICAL COMPO ONENT TECH HNOLOGIES 231 suspended membrane microbridge was developed at CEA-Let along with a terahertz an d m w ti, h ntenna designn based on crossed anten c nnas and a ressonant cavity, as shown in Figure 4-44. Arrays of 320 × 240 0 microbolo ometers were collectively processed at video frame r p v rates above CMMOS wafers by integration with a CEEA-Leti design applicatio ned on-specific in ntegrated circu The estim uit. Read the entire page →
From page 232... ... 232 LASER RADAR BEAM STEERING AND STABILIZATION Active EO sensors need to point and stabilize the transmit beam and the receiver field of view. Gimbals are mechanically complex and expensive but can steer very accurately over wide angles. Read the entire page →
From page 233... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 233 FIGURE 4-47 Early Lockheed Martin Risley prism. SOURCE: Courtesy of Dennis J Read the entire page →
From page 234... ... 234 LASER RADAR FIGURE 4-48 Modulo 2π beam steering at the design wavelength. SOURCE: Copyright 2013 IEEE. Read the entire page →
From page 235... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 235 FIGURE 4-49 Reset limitations due to fringing fields. SOURCE: Copyright 2013 IEEE. Read the entire page →
From page 236... ... 236 LASER RADAR the wavelength, steering can be done to about 1/8th radian, or about 7 degrees. In one example, 152 the chip is only about 576 μm -- a very small aperture. Read the entire page →
From page 237... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 237 . FIGURE 4-50 Voltage-tunable liquid crystal waveguide based in-plane steering. Read the entire page →
From page 238... ... 238 LASER RADAR Larger angles are reached using a set of binary birefringent prisms. One polarization sees the prism deflecting the beam in one direction, while the other sees the prism deflecting it the other way. Read the entire page →
From page 239... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 239 Pointing and stabilizing to very small angles is an expensive proposition, involving large optics. The newest methods of pointing and stabilization will be seen in the literature. Read the entire page →
From page 240... ... 240 LASER RADAR FIGURE 4-52 Evolution of cryocooler and IR detector packaging. IDCA, integrated detector/cooler assembly. Read the entire page →
From page 241... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 241 FIGURE 4-53 Common module cryogenic cooler of 1 W SOURCE: DRS Technologies, Dallas, Texas. Read the entire page →
From page 242... ... 242 LASER RADAR FIGURE 4-54 Linear drive compressor approach. SOURCE: DRS Technologies, Dallas, Texas. Read the entire page →
From page 243... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 243 FIGURE 4-56 Components of a Dewar. Read the entire page →
From page 244... ... 244 LASER RADAR commonly silicon, BK7 glass, sapphire, and germanium. Key to coldfilter performance is high transmission in the range of interest and high rejection outside that band. Read the entire page →
From page 245... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 245 FIGURE 4-58 Advanced integrated Dewar cooler FIGURE 4-59 High-operating-temperature IDCA assembly. SOURCE: DRS Technologies, Dallas, Texas. Read the entire page →
From page 246... ... 246 LASER RADAR ADAPTIVE OPTICS As will be described in more detail in Chapter 5, the atmosphere affects active EO sensors in three main ways: absorption, scattering, and refractive index variations (which can cause beam spreading or fluctuations) Read the entire page →
From page 247... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 247 Another issue for an adaptive optics system may be having a point source to use as a guide for finding the optimum phase corrections. Sometimes an artificial point source is created, called a guide star. Read the entire page →
From page 248... ... 248 LASER RADAR TABLE 4-5 PED Requirements Versus Selected Application Domains Application Possible platform Processing Exploitation Dissemination Surveillance UAV Image formation Precise positions High bandwidth and refinement, for objects and desirable, but not image/video actors in real-time easily achievable selection and with RF compression Mapping Airborne imager 3-D image Precise 3-D maps Can be gathered formation, of terrain, e.g., and stored until registration to knit urban terrain return to base multiple swaths together Local navigation Driverless Image formation Avoiding obstacles Not applicable; automobile in real time intended for local use FIGURE 4-61 Abstract model of steps from detector to analyst. SOURCE: National Research Council, 2010, Seeing Photons: Progress and Limits of Visible and Infrared Sensor Arrays, The National Academies Press, Washington, D.C., Figure 4-9. Read the entire page →
From page 249... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 249 Various processing schemes can be employed, from tracking classified objects (object classification is discussed in the section below) to simply tracking centroids of moving objects. Read the entire page →
From page 250... ... 250 LASER RADAR Leachtenauer et al. later used the same empirical methodology applied to infrared images. Read the entire page →
From page 251... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 251 Data File Size, Compression, Dissemination, and Communication Bandwidth Requirements A given sensor produces data at some rate, and then the application domain dictates whether data is stored or communicated. Whether stored or communicated, it may be compressed to a more compact form, ideally with minimal loss of information content. Read the entire page →
From page 252... ... 252 LASER RADAR FIGURE 4-63 ALIRT data processing steps. Read the entire page →
From page 253... ... ACTIVE ELECTRO-OPTICAL COMPONENT TECHNOLOGIES 253 TABLE 4-6 Computing Resources Consumed per Second of Imagery Algorithm Task Processing Time/Real Time Raw data input 0.1 Cartesian integration 3.0 Ground detection 0.2 Response deconvolution 3.2 Static voxel determination 1.1 XYZ file output 0.7 Total 8.2 NOTE: Single processor timing results measured on a 3 GHz Pentium machine. SOURCE: Peter Cho, Hyrum Anderson, Robert Hatch, and Prem Ramaswami, 2006, "Real-time 3D ladar imaging," Lincoln Laboratory Journal, 16(1) Read the entire page →
From page 254... ... 254 LASER RADAR Currently, data from high-performance ladar sensors requires parallel processing. Processing capabilities with abundant parallelism, such as many core graphics processor units (GPUs) Read the entire page →

From page 154...

... 4 Active Electro-Optical Component Technologies As has been described in Chapters 2 and 3, current and emerging active electro-optical (EO) sensing systems are implemented in many different modalities.