Showing papers on "High dynamic range published in 1993"

High dynamic range third-order correlation measurement of picosecond laser pulse shapes

Abstract: A third-order correlation system has been developed, which enables the contrast ratio of high-intensity ultra-short laser pulses to be measured on a single shot, with a dynamic range of better than 108.

Intermodulation distortion in high dynamic range microwave fiber-optic links with linearized modulators

Abstract: Linearization of integrated optic intensity modulators significantly reduces the two-tone intermodulation distortion. The resulting intermodulation distortion produced by these modulators then varies as the input power to the fifth-order link system, the overall intermodulation product is a combination of third-order and higher-order terms. The authors determine the dynamic range of a cascaded microwave network consisting of a preamplifier, a high-dynamic-range fiber-optic link with a highly linear modulator, and a postamplifier. An expression is found that relates the intermodulation power at the output to the relative suppression from the signal level. As an example, a hypothetical 10-GHz low-distortion fiber-optic link that has a dynamic range of 125 dB in a bandwidth of 1 Hz is cascaded with various preamplifiers, and it is shown that the dynamic range of the system is reduced by as much as 20 dB, depending on the third-order intercept of the amplifier.

Frequency selective limiters for high dynamic range microwave receivers

Abstract: A broadband frequency selective limiter (FSL) which provides over 14 dB of limiting across more than an octave bandwidth is described The limiter is fabricated with epitaxially grown YIG (yttrium iron garnet) films in a stripline configuration and has a threshold power level of below 0 dBm Individual limiter strips limit microwave signals in the 1-100-mW range across more than an octave of bandwidth Multiple FSLs have been cascaded with amplifiers to allow compression of microwave signals with a power range of 60 dB into a range of less than 5 dB >

High dynamic range passive optical limiters

Abstract: We present results of optical limiting experiments designed to study optical geometries for increasing the dynamic range over which limiters function without incurring optical damage. Specifically, we investigate a tandem geometry with two passive nonlinear elements, one placed in the focal plane of a lens and the second placed “upstream” of the focal position to protect the material at focus from damage. To provide a proof-of-principle demonstration of this geometry, simple limiters consisting of combinations of reverse saturable absorber dyes and a carbon black suspension in thin cells were tested. Our results show that a substantial increase in device performance can be achieved by use of a tandem limiter geometry. Simple modelling predicts that the dynamic range of a separate-element tandem limiter is given by the product of the dynamic ranges of the individual component limiting elements, in agreement with our experimental results.

Josephson sigma-delta modulator for high dynamic range A/D conversion

Abstract: A Josephson sigma-delta modulator suitable for use in high dynamic range conversion of MHz bandwidth signals was designed and simulated. Input signal voltages were integrated as current in a superconducting inductor. A single junction quantizer provided analog-to-digital (AID) conversion at 40 GHz and fed back single-flux-quantum (SFQ) voltage pulses to balance the input. A JSIM calculation for a 13,110,000-ps interval indicated ideal first-order noise shaping of a 2.44-MHz voltage-source signal. Spur free dynamic range was 102 dB and signal-to-noise-and-distortion was 98 dB on the DC 10-MHz signal band, equivalent to a 16-b, 20-MSample/s, Nyquist-rate A/D. The modulator transfer function was derived for a current-source signal applied to an input resistor. First-order quantization noise suppression was still observed for signal bands wider than the 2 pi R/L modulator cutoff frequency. The superconductive sigma-delta modulator combines the speed of Josephson junctions for GHz sampling and digital filtering with the quantum mechanical accuracy of SFQ feedback to obtain superior A/D performance. >

Glacier study using wavenumber domain synthetic aperture radar

Abstract: New developments of frequency synthesizers and digital phase detectors make it possible to produce digital radars with high dynamic range that operate in the frequency domain. These radars are especially well suited for ground-penetrating use. This contribution presents the theoretical basis for frequency domain radars and develops a wavenumber domain-based synthetic aperture radar algorithm for inverting the data. The effect of the propagation medium is taken into account, and experimental results from a subpolar glacier are given.

Multi-resonant electronic power converter with a wide dynamic range

Abstract: Methods and apparatus for variably converting a DC voltage to a different DC voltage level are effected by a multi-resonant electronic power converter with a wide output voltage dynamic range. The power conversion is accomplished by converting the DC voltage to an AC signal, adjusting or attenuating the AC signal to the desired amplitude, and then converting the AC signal back to a DC voltage. The output voltage may be adjusted by altering the frequency of the AC signal also known as the switching frequency. A wide dynamic range is achieved at a narrow switching frequency bandwidth by inserting either a fourth or higher order low pass filter or a notch filter at the output of the switching transistor. The high roll-off rate exhibited by either filter provides a relatively high dynamic range in a narrow frequency range.

High-dynamic-range x-ray imager employing CdZnTe detector arrays

Abstract: We have designed and fabricated an x-ray linear scanner based on monolithic CdZnTe arrays. The arrays are 1.0 inch long with 16 detectors each. To increase the x-ray stopping power of the arrays, they are operated with the x-ray photons incident normal to the E-field direction. A photon-counting pulse mode read-out is utilized to produce high dynamic range images at low incident flux rates. Our read-out electronics are composed of independent 16-channel modules including charge pre-amplification, pulse shaping discriminated scaler, and buffered I/O. The linear packing density for the electronics is 16 channels per inch, commensurate with the array pitch. Results from measurements of spatial response generated by scanning a fine beam of gamma rays across the arrays, and x-ray images produced in a linear-scan mode are presented.

Performance of a flux locked series SQUID array

Abstract: The operation of a SQUID array with 100 DC SQUIDs has been demonstrated using a single flux-locked loop. The SQUID array had a maximum dynamic range of +or-1.3*10/sup 8// square root (Hz) in the low frequency region, a high slewing rate over a wide frequency range, and an extrinsic white noise energy sensitivity of 6*10/sup -31/J/Hz. These data were obtained with a very simple feedback circuit made from three inexpensive operational amplifiers that operated in the DC-feedback mode. The feedback loop did not have any impedance matching circuit between the SQUID array and the room temperature electronics. Our results show that a SQUID array can have a significant impact on those applications that demand good noise performance and a very high dynamic range. >

Low-cost, high-resolution x-ray detector system for digital radiography and computed tomography

Abstract: We have designed and evaluated a novel design of line array x-ray detector for use with digital radiography (DR) and computed tomography (CT) systems. The Radiographic Line Scan (RLS) detector is less than half the cost of discrete multi-channel line array detectors, yet provides the potential for resolution to less than 25 micrometers at energies of 420 kV. The RLS detector consists of a scintillator fiber-optically coupled to a thermo-electrically cooled line array CCD. Gadolinium oxysulfide screen material has been used as the scintillator, in thicknesses up to 250 micrometers . Scintillating glass, which is formed into a fiber optic bundle, has also been used in thicknesses up to 2 mm. The large 2.5 mm by 25 micrometers CCD cells provide high dynamic range while preserving high resolution; the 2.5 mm dimension is oriented in the x-ray absorption direction while the 25 micrometers dimension is oriented in the resolution direction. Servo controlled thermo-electric cooling of the CCD to a fixed temperature provides reduction of dark current and stabilization of the output. Greater dynamic range is achieved by reducing the dark current, while output stabilization reduces the need for frequent calibration of the detector. Measured performance characteristics are presented along with DR and CT images produced using the RLS detector.

A 20 GHz bandwidth InGaAsP/InP MTBH laser module

Abstract: A 1.3- mu m InGaAsP/InP straight-wall mass-transport buried heterostructure (MTBH) laser diode was designed and fabricated to operate over a bandwidth of 20 GHz. The laser when used in a microwave link has an RF insertion loss of 37 dB, an equivalent input noise density of less than -115 dBm/Hz, input power at 1 dB compression greater than 23 dBm and a spurious signal free dynamic range of 97 dB-Hz/sup 2/3/. The wide bandwidth, high dynamic range, and low noise of the laser module were obtained through the design of the package, the subcarrier, and the laser chip. >

Diode laser arrays for dynamic infrared scene projection

Abstract: A novel concept for dynamic IR scene projection using IR diode lasers has been developed. This technology offers significant cost and performance advantages over other currently available projector technologies. Performance advantages include high dynamic range, multiple wavebands, and high frame rates. A projector system which utilizes a 16-element linear array has been developed and integrated into the millimeter wave/infrared (MMW/IR) hardware-in-the-loop (HWIL) facility at the US Army Missile Command's (USAMICOM's) Research, Development, and Engineering Center (RDEC). This projector has demonstrated dynamic range in excess of 105, apparent temperatures greater than 2500 degree(s)C, and nanosecond response times. Performance characteristics for this projector system are presented in the paper. Designs for projectors to test other IR sensor configurations, including FPAs, have been developed and are presented as well. The FPA design consists of a linear array of diode lasers scanned by a polygon mirror. This low-cost projector offers high resolution, high contrast 2-D scenes at up to 10 KHz frame rates. Simulation of active IR countermeasures is another promising application of diode laser projector systems. The diode laser is capable of simulating flares or virtually any IR jammer waveform.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A novel analog optical link with high dynamic range

Abstract: A heterodyne interferometric phase modulated link, a new analog optical link, is described. This link, based on phase modulation using an external modulator, has high linearity and suppresses the impact of laser relative intensity noise. The link increases the spurious-free dynamic range by 21 dB as compared to a conventional externally modulated AM link for 10 mW of received optical power, relative intensity noise of -130 dB/Hz, and a 15-GHz intermediate frequency. >

Filter transmittance measurements in the infrared

Abstract: We have set up a novel direct detection system to measure filter transmittances over an attenuation range of at least 5 decades, with relative combined standard uncertainties as low as 0.5% (Icr) per decade, in the 9 ju,m to 11 /im spectral region. This system, using an apparatus originally designed for a heterodyne measurement of transmittance, achieves higher accuracy at the expense of a reduced dynamic range. This independent measurement of transmittance allows verification of the heterodyne technique. Our system uses a source modulated at 30 MHz and a specially constructed high dynamic range and high accuracy lock-in amplifier capable of operation at the modulation frequency. The high modulation frequency and narrow bandwidth of the system allow thermal background radiation to be suppressed and high accuracy to be achieved. We correct for the non-ideal natures of the detector and attenuators. In particular, the detector position is scanned to reduce the effect of its spatial nonuniformily and the deflection of the transmitted beam caused by the nonparallel surfaces of the filter. We discuss the sources of systematic errors and the methodology to reduce their contribution.

A low noise optical receiver for a 155 Mbit/s 4 km optical free space link

Abstract: The optimum design and resultant performance of a direct detection optical receiver for a terrestrial line of sight free space application has been outlined. The good sensitivity and high dynamic range of the bootstrapped preamplifier have allowed the establishment of an experimental 155.52 Mbit/s link over a 4 km path in London. >

Frequency selective limiters for high dynamic range microwave receivers

Abstract: A novel broadband frequency selective limiter (FSL) which provides over 14 dB of limiting across more than an octave bandwidth is described. The limiter is fabricated with epitaxially grown YIG (yttrium iron garnet) films in a stripline configuration and has a threshold power level of below 0 dBm. Individual limiter strips limit microwave signals in the 1-100-mW range. Multiple FSLs have been cascaded with amplifiers to allow compression of microwave signals with a power range of 60 dB into a range of less than 5 dB. >

High-Dynamic Range Fiberoptic Links for Antenna Remoting Applications

Abstract: In recent years, the performance and cost effectiveness of analog fiberoptic communication systems have improved so that many applications including antenna remoting which requires high dynamic range can now benefit from the many advantages of fiber optics.

Megapixel high-dynamic-range low-energy x-ray imager for synchrotron applications

Abstract: New synchrotron facilities such as the European Synchrotron Radiation Facility rely on the development of new detectors to take full advantage of the dramatic increase in the brilliance of their x-ray beamlines. A novel detector system based on modified x-ray image intensifiers (XRII) optically coupled to CCD cameras is described. Different options fit specific requirements, essentially trading resolution against speed. The energy range covers from 5 to 25 keV with the special beryllium windowed XRII, and up to 100 keV with standard medical imager tubes. Input size is 200 mm in diameter, with electronic zooming capability down to (phi) 100 mm. A 50% MTF is reached for 17 line pairs/cm. More important is the extremely narrow wings of the point spread function: full width at 0.1% of maximum is less than 1 mm. Noise is negligible in most applications, being equivalent to a few x-ray photons/s.cm2, so that single x-ray photons are easily distinguished. Commercially available slow scan CCD cameras allow 16 bit dynamic range megapixel images to be read-out in 10 - 20s. Faster designs studied at the ESRF using multi-output CCD already make it possible to acquire several images per second, and ultra fast systems with only 512 X 512 pixels are expected to reach up to 300 images/s while maintaining a dynamic range of 1000:1.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Semiconductor lasers for analog applications

Abstract: In almost every area of communications, the trend is to replace analog transmission with digital. At the same time, the demand for DFB lasers capable of meeting high dynamic range analog characteristics has grown dramatically. In this paper, this apparent contradiction will be examined and some of the many applications for which high dynamic range links are being used will be reviewed. >

High-resolution CCD camera family with a PC host

Abstract: EG&G Reticon and Adaptive Optics Associates have developed a family of high resolution CCD cameras with a PC/AT host to fulfill imaging applications from medical science to industrial inspection. The MC4000 family of CCD cameras encompasses resolutions of 512 X 512, 1024 X 1024, and 2048 X 2048 pixels. All three of these high performance cameras interface to the SB4000, PC/AT controller, which serves as a frame buffer with up to 64 MBytes of storage, as well as providing all the required control, and setup parameters while the camera head is remotely located at distances of up to 100 ft. All of the MC4000 high resolution cameras employ MPP clocking to achieve high dynamic range without cooling the CCD sensor. The use of this low power clocking technique, surface mount components, electronic shutter and clever packaging have allowed Reticon to deliver the MC4000 cameras in convenient, rugged small housings. The MC4000 family provides users with a total imaging solution from leading edge sensors and electronics in ruggedized housings, to cables, power supplies, and a PC/AT frame buffer and controller card. All the components are designed to function together as a turn-key, self-contained system, or individual components can become part of a user's larger system. The MC4000 CCD camera family makes high resolution, electronic imaging an accessible tool for a wide range of applications.

Multilayer anode with orthogonal serpentine delay lines for high-spatial-resolution readout of microchannel plate detectors

Abstract: We have designed, built, and tested the first successful imaging microchannel-plate (MCP) detector that uses two orthogonal, printed circuit, serpentine delay lines in a three-dimensional architecture. Laser-ablation machining is used to cut slots that allow delay lines in two layers parallel to the MCP to sample and read out x and y image positions. Previous anodes that use delay-line timing to read out both dimensions of an image employ a wire-would anode. The goal of this readout is to provide as many picture elements (pixels) as possible in two dimensions, with high temporal resolution, high throughput, high dynamic range, and good spatial linearity. This detector achieves this goal with off-the-shelf electronics and is robust for space flight. The full width half maximum spatial resolution is 32 micrometers at the center of the detector and is typically < 35 micrometers throughout the detector. The rms linearity is 40 micrometers in each readout dimension, after applying only radial corrections for fringe field effects near the perimeter, and < 20 micrometers after applying additional simple (1- dimensional) corrections. We discuss fabrication techniques.

Fast Optical Imaging Techniques

Abstract: The distinction between detectors for imaging and spectroscopy is becoming increasingly blurred. The use of two-dimensional detectors to allow the recording of many spectra simultaneously is rapidly becoming an essential part of many experimental set-ups where the requirement is to look at temporal or spatial spectral variations within one experiment. In many applications there is a need for good time resolution. Traditional systems are used that operate at the rate of 50 or 60 Hz commonly used by standard TV cameras. This paper will look at the limitations that are encountered in trying to take fluorescent images at much higher repetition (frame) rates.

High speed characterization of pseudomorphic HEMT structures using a very low noise scintillation detector

Abstract: We show that a very low noise, high dynamic range scintillation detector has major advantages over conventional detectors for characterization of pseudomorphic HEMT structures by high resolution X-ray diffraction. We show that the reduced background enables a second modulation period to be detected, enabling the thickness and composition to be determined independently. Using a conventional X-ray generator and diffractometer we demonstrate that, in a single scan taking only 10 seconds, we are able to obtain sufficiently good data to provide quality assurance. 4 refs., 6 figs.

A comparison of three analog optical links for high dynamic range applications

Abstract: A new heterodyne interferometric phase modulation (HIPM) link and a new subcarrier frequency modulation with direct detection (SFM-DD) link are proposed. To generate angle-modulated signals at the receiver, the HIPM system utilize a novel external modulator, while the SFM-DD system uses electronic preprocessing. The spurious free dynamic ranges (SFDR) of the SFM-DD and HIPM systems are larger than that of the amplitude modulation with direct detection (AMDD) system; when relative intensity noise (RIN) is dominant, these two systems can show 26 dB and 28 dB advantages with respect to the AMDD system, respectively. >

High Dynamic Range Fiber Optic Link Measurements With Traveling Wave Linearized Directional Coupler Modulators

Abstract: An important figure of merit for all high frequency analog transmission links is the spur free dynamic range (SFDR) which is the ratio of the largest to smallest signal that the link can transmit and receive without introducing distortion. The two factors which limit the dynamic range in fiber optic links are the system noise, predominantly from the laser relative intensity noise and the photodetector shot noise, and the non-linearity of the modulation process. The noise level of fiber optic systems has been reduced as much as possible for now through the use of high-power solid state or DFB lasers and attention has turned to improving the linearity of the modulation.