Video signal enhancement system with dynamic range compression and modulation index expansion Patent
Video signal enhancement of signal component representing brightness of scene element in low contrast
Wong, R. Y.↗
SEARCH · Search NASA
Results for “Dynamic range”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Wide-range dynamic pressure sensor
Transducer measures pressure by sensing the damping of a vibrating diaphragm immersed in the atmosphere to be measured. Improved sensor can be included in rugged, lightweight package for use aboard aircraft, meteorological vehicles, and space probes.
Dimeff, J.↗
Overlap diffusion for increasing phototransistor dynamic range
Construction of improved phototransistors to provide increased base-collector capacitance is described. Silicon or germanium semiconductor wafers are used as examples. Operation of transistors and electrical properties are discussed and illustrations of the devices are included.
Mccann, D. H.↗
Wide-dynamic-range detector
Circuit drives diode detector with amplifier having high and constant output impedance. Basic circuit could be used in high-performance AM radios, tape players, and phonographs.
Matheson, R. J.↗
Logarithmic circuit with wide dynamic range
A circuit deriving an output voltage that is proportional to the logarithm of a dc input voltage susceptible to wide variations in amplitude includes a constant current source which forward biases a diode so that the diode operates in the exponential portion of its voltage versus current characteristic, above its saturation current. The constant current source includes first and second, cascaded feedback, dc operational amplifiers connected in negative feedback circuit. An input terminal of the first amplifier is responsive to the input voltage. A circuit shunting the first amplifier output terminal includes a resistor in series with the diode. The voltage across the resistor is sensed at the input of the second dc operational feedback amplifier. The current flowing through the resistor is proportional to the input voltage over the wide range of variations in amplitude of the input voltage.
Wiley, P. H.↗
Investigation of the dynamic range problem and providing software support for the AOL system
The present scheme for providing system timing for the airborne oceanographic lidar (AOL) system is not completely satisfactory. The possibility of using a digital approach to generate the forty pulses needed to energize the gates leading to the charge digitizers was investigated. The solution in terms of general analog and digital circuitry is straightforward. The crystal oscillator provides a stable frequency source which is used as a clock to the ring counter. The ring counter propagates a pulse from stage one to stage forty. Each of the outputs has an amplifier for isolation. This design is easy to implement in the frequency range up to 50 MHZ. Because a gate pulse width of from about 2 to 6 ns is needed for the AOL system, this dictates an input clock frequency to the shift register of from 100 MHA to 500 MHA. Problems associated with generating pulses in this range of operation are examined and an alternate solution is discussed.
Source record↗
Schottky diode mm detectors with improved sensitivity and dynamic range
A detector which features a low-barrier Si Schottky diode is discussed. The unbiased diode has a sensitivity of -60 dBm and a range of 50 dB at 95 GHz, and fixed tuning yields a sensitivity within 2 dB from 75-110 GHz. A limitation of the low-barrier diode is a reduction in the low-level sensitivity by 16 dB under a 100 kilohms load. Use of the diode with a video impedance of 120 kilohms enables the offset voltage to be nulled with an appropriate control. Operation of the diode in a waveguide mount for use as a mixer is described, along with detector rectification.
Kerr, A. R.↗
Information for space radar designers: Required dynamic range vs resolution and antenna calibration using the Amazon rain forest
Calibration of the vertical pattern of the antennas for the SEASAT scatterometer was accomplished using the nearly-uniform radar return from the Amazon rain forest. A similar calibration will be attempted for the SIR-B antenna. Thick calibration is important to establish the radiometric calibration across the swath of the SIR-B, and the developed methodology will provide an important tool in the evaluation of future spaceborne imaging radars. This calibration was made by the very-wide-beam SEASAT scatterometer antennas because at 14.65 GHz the scattering coefficient of the rain forest is almost independent of angle of incidence. It is expected that the variation in scattering coefficient for the rain forest across the relatively narrow vertical beam of the SIR-B will be very small; even at L band the forest should be essentially impenetrable for radar signals, the volume scatter from the treetops will predominate as at higher frequencies. The basic research elements include: (1) examination of SIR-B images over the rain forest to establish the variability of the scattering coefficient at finer resolutions than that of the SEASAT scatterometer; (2) analysis of the variability of SIR-B data detected prior to processing for either azimuth compression or; possibly, range compression so that averages over relatively large footprints can be used; (3) processing of data of the form of (2) using algorithms that can recover the vertical pattern of the antenna.
Moore, R. K.↗
Dynamic range compression/expansion of light beams by photorefractive crystals
Apparatus is provided which greatly reduced the intensity of bright portions of an image while only moderately reducing the brightness of dimmer portions of the image, to thereby compress the range of light intensities to facilitate detection of the image. The apparatus includes a light detector device formed by a chip of photorefractive material. A two-dimensional array of light beams from an object to be detected, passes through a beam splitter to form two arrays of light beams. The two arrays of light beams are directed at different angles against a surface of the chip of photorefractive material, the two arrays of light beams forming coincident images on the surface. One of the the two-dimensional arrays of beams emerging from an opposite surface of the chip has a lower range of intensities, to facilitate detection of the object despite very bright spots on its image. The other array of light beams emerging from the chip has a greater range of intensities than the unprocessed image of the object.
Li-Jen Cheng↗
Infrared pre-detection dynamic range compression via photorefractive crystals
Explore the source record for details and available documents.
Liu, Hua-Kuang↗
Fiber-Optic Coupler And Dynamic-Range Enhancer For CARS
Simpler equipment yields higher coupling efficiency with fewer adjustments. In improved scheme for coupling coherent anti-Stokes Raman spectroscopy (CARS) signal from measurement volume to monochromator, optical fiber and two lenses used in place of previous system. Cylindrical lenses focus light from optical fiber into beam of approximately rectangular cross section at input plane of monochromator. Optical wedge diverts part of beam in monochromator to produce less-intense secondary image.
Cutler, Andrew D.↗
High-Dynamic-Range Fiber-Optic Link For Microwave Signals
Ultrastable fiber-optic communications system transmits microwave signals between antenna sites of Deep Space Network (DSN) and central processing station several kilometers away. Permits relocation of critical components from front-end areas of DSN antennas to central location, permitting radio-frequency (RF) antenna arraying, improving DSN flexibility, maintainability, and system performance. Also useful in commercial analog and digital communications.
Logan, Ronald T., Jr.↗
High Resolution and Large Dynamic Range Resonant Pressure Sensor Based on Q-Factor Measurement
A pressure sensor has a high degree of accuracy over a wide range of pressures. Using a pressure sensor relying upon resonant oscillations to determine pressure, a driving circuit drives such a pressure sensor at resonance and tracks resonant frequency and amplitude shifts with changes in pressure. Pressure changes affect the Q-factor of the resonating portion of the pressure sensor. Such Q-factor changes are detected by the driving/sensing circuit which in turn tracks the changes in resonant frequency to maintain the pressure sensor at resonance. Changes in the Q-factor are reflected in changes of amplitude of the resonating pressure sensor. In response, upon sensing the changes in the amplitude, the driving circuit changes the force or strength of the electrostatic driving signal to maintain the resonator at constant amplitude. The amplitude of the driving signals become a direct measure of the changes in pressure as the operating characteristics of the resonator give rise to a linear response curve for the amplitude of the driving signal. Pressure change resolution is on the order of 10(exp -6) torr over a range spanning from 7,600 torr to 10(exp -6) torr. No temperature compensation for the pressure sensor of the present invention is foreseen. Power requirements for the pressure sensor are generally minimal due to the low-loss mechanical design of the resonating pressure sensor and the simple control electronics.
Gutierrez, Roman C.↗
Comparison of high dynamic range: near-neighbor detection approaches for TPF
We discuss the detection of planets around neighboring stars and current technology.
TPF near neighbor detection↗
CMOS APS Image Sensor with Ultra-High Linear-Dynamic-Range Utilizing Dual Output
Explore the source record for details and available documents.
Image Sensor↗
Motor Controller System For Large Dynamic Range of Motor Operation
A motor controller system uses a rotary sensor with a plurality of signal conditioning units, coupled to the rotary sensor. Each of these units, which is associated with a particular range of motor output shaft rotation rates, generate a feedback signal indicative of the position of the motor s output shaft. A controller (i) converts a selected motor output shaft rotation rate to a corresponding incremental amount of rotational movement for a selected fixed time period, (ii) selects, at periodic completions of the selected fixed time period, the feedback signal from one of the signal conditioning units for which the particular range of motor output shaft rotation rates associated therewith encompasses the selected motor output shaft rotation rate, and (iii) generates a motor drive signal based on a difference between the incremental amount of rotational movement and the feedback signal from the selected one of the signal conditioning Units.
Howard, David E.↗
Conductance measurement circuit with wide dynamic range
A conductance measurement circuit to measure conductance of a solution under test with an output voltage proportional to conductance over a 5-decade range, i.e., 0.01 uS to 1000 uS or from 0.1 uS to 10,000 uS. An increase in conductance indicates growth, or multiplication, of the bacteria in the test solution. Two circuits are used each for an alternate half-cycle time periods of an alternate squarewave in order to cause alternate and opposite currents to be applied to the test solution. The output of one of the two circuits may be scaled for a different range optimum switching frequency dependent upon the solution conductance and to enable uninterrupted measurement over the complete 5-decade range. This circuitry provides two overlapping ranges of conductance which can be read simultaneously without discontinuity thereby eliminating range switching within the basic circuitry. A VCO is used to automatically change the operating frequency according to the particular value of the conductance being measured, and comparators indicate which range is valid and also facilitate computer-controlled data acquisition. A multiplexer may be used to monitor any number of solutions under test continuously.
Mount, Bruce E.↗
Power supply with air core transformer and seperated power supplies for high dynamic range
A power supply for a quadrupole mass spectrometer which operates using an RF signal. The RF signal is controllable via a feedback loop. The feedback loop is from the output, through a comparator, and compared to a digital signal. An air core transformer is used to minimize the weight. The air core transformer is driven via two out of phase sawtooth signals which drive opposite ends of the transformer.
Chutjian, Ara↗