Showing papers on "Dynamic range published in 2013"

A 128 $\,\times$ 128 1.5% Contrast Sensitivity 0.9% FPN 3 µs Latency 4 mW Asynchronous Frame-Free Dynamic Vision Sensor Using Transimpedance Preamplifiers

Abstract: Dynamic Vision Sensors (DVS) have recently appeared as a new paradigm for vision sensing and processing. They feature unique characteristics such as contrast coding under wide illumination variation, micro-second latency response to fast stimuli, and low output data rates (which greatly improves the efficiency of post-processing stages). They can track extremely fast objects (e.g., time resolution is better than 100 kFrames/s video) without special lighting conditions. Their availability has triggered a new range of vision applications in the fields of surveillance, motion analyses, robotics, and microscopic dynamic observations. One key DVS feature is contrast sensitivity, which has so far been reported to be in the 10-15% range. In this paper, a novel pixel photo sensing and transimpedance pre-amplification stage makes it possible to improve by one order of magnitude contrast sensitivity (down to 1.5%) and power (down to 4 mW), reduce the best reported FPN (Fixed Pattern Noise) by a factor of 2 (down to 0.9%), while maintaining the shortest reported latency (3 μs) and good Dynamic Range (120 dB), and further reducing overall area (down to 30 × 31 μm per pixel). The only penalty is the limitation of intrascene Dynamic Range to 3 decades. A 128 × 128 DVS test prototype has been fabricated in standard 0.35 μm CMOS and extensive experimental characterization results are provided.

Displacement Sensor Based on Diamond-Shaped Tapered Split Ring Resonator

Abstract: Split-ring resonators (SRRs) are ideal structures for the realization of compact high-sensitivity and high-resolution sensors due to their high-quality factor resonance, compact size, and high sensitivity to changes in the constituent materials and physical dimensions. This paper presents a displacement sensor based on a diamond-shaped tapered SRR coupled to a coplanar waveguide. Two significant improvements over previous designs are reported. Firstly, the proposed sensor has higher dynamic range and linearity for displacement sensing. Secondly, compared with previous designs, where the displacement changes both the resonant frequency and depth of the transmission notch, the proposed sensor has a fixed resonant frequency. This is an important improvement since the sensor can be operated at a single fixed frequency and bypass the need for a frequency-sweeping microwave source and measurement system such as an expensive network analyzer. It is shown that, while preserving the compact size, the proposed sensor also benefits from a lower operating frequency. The design principle and simulation results are validated through measurement.

Systems and methods for extending dynamic range of imager arrays by controlling pixel analog gain

Abstract: Array cameras and imager arrays configured to capture high dynamic range light field image data and methods of capturing high dynamic range light field image data in accordance with embodiments of the invention are disclosed. Imager arrays in accordance with many embodiments of the invention include multiple focal planes with associated read out and sampling circuitry. The sampling circuitry controls the conversion of the analog image information into digital image data. In certain embodiments, the sampling circuitry includes an Analog Front End (AFE) and an Analog to Digital Converter (ADC). In several embodiments, the AFE is used to apply different amplification gains to analog image information read out from pixels in a given focal plane to provide increased dynamic range to digital image data generated by digitizing the amplified analog image information. The different amplifications gains can be applied in a predetermined manner or on a pixel by pixel basis.

A 0.45 V 100-Channel Neural-Recording IC With Sub- $\mu {\rm W}$ /Channel Consumption in 0.18 $\mu{\rm m}$ CMOS

Abstract: Neural prosthetics and personal healthcare have increasing need of high channel density low noise low power neural sensor interfaces. The input referred noise and quantization resolution are two essential factors which prevent conventional neural sensor interfaces from simultaneously achieving a good noise efficiency factor and low power consumption. In this paper, a neural recording architecture with dynamic range folding and current reuse techniques is proposed and dedicated to solving the noise and dynamic range trade-off under low voltage low power operation. Measured results from the silicon prototype show that the proposed design achieves 3.2 μVrms input referred noise and 8.27 effective number of bits at only 0.45 V supply and 0.94 μW/channel power consumption.

Modeling the Performance of Single-Bit and Multi-Bit Quanta Image Sensors

Abstract: Imaging performance metrics of single-bit and multi-bit photo-electron-counting quanta image sensors (QIS) are analyzed using Poisson arrival statistics. Signal and noise as a function of exposure are determined. The D-log H characteristic of single-bit sensors including overexposure latitude is quantified. Linearity and dynamic range are also investigated. Read-noise-induced bit-error rate is analyzed and a read-noise target of less than 0.15 e-rms is suggested.

The feasibility of a piecewise-linear dynamic bowtie filter

Abstract: Purpose: The prepatient attenuator (or “bowtie filter”) in CT is used to modulate the flux as a function of fan angle of the x-ray beam incident on the patient. Traditional, static bowtie filters are tailored only for very generic scans and for the average patient. The authors propose a design for a dynamic bowtie that can produce a time-dependent piecewise-linear attenuation profile. This dynamic bowtie may reduce dynamic range, dose or scatter, but in this work they focus on its ability to reduce dynamic range, which may be particularly important for systems employing photon-counting detectors. Methods: The dynamic bowtie is composed of a set of triangular wedges. Each wedge is independently moved in order to produce a time-dependent piecewise-linear attenuation profile. Simulations of the bowtie are conducted to estimate the dynamic range reduction in six clinical datasets. The control of the dynamic bowtie is determined by solving a convex optimization problem, and the dose is estimated using Monte Carlo techniques. Beam hardening artifacts are also simulated. Results: The dynamic range is reduced by factors ranging from 2.4 to 27 depending on the part of the body studied. With a dynamic range minimization objective, the dose to the patient can be reduced from 6% to 33% while maintaining peak image noise. Further reduction in dose may be possible with a specific dose reduction objective. Beam hardening artifacts are suppressed with a two-pass algorithm. Conclusions: A dynamic bowtie producing a time-dependent, piecewise-linear attenuation profile is possible and can be used to modulate the flux of the scanner to the imaging task. Initial simulations show a large reduction in dynamic range. Several other applications are possible.

High Dynamic Range Organic Temperature Sensor

Abstract: IC A IO N Due to the compatibility with large-area fabrication techniques and low fabrication costs involved, organic transistors have been actively researched and various kinds of chemical or physical sensors based on organics transistors have been developed. These sensors can be used for the detection of moisture, [ 1 ] glucose, [ 2 ] pressure, [ 3 , 4 ] light intensity, [ 5 ] and temperature. [ 3b ] For pressure-sensing applications, Bao et al. have demonstrated micro-structured polydimethylsiloxane (PDMS) pressure sensors with sensitivity down to 3 Pa. Someya et al. have also prepared pressure-sensor arrays with memory properties by using pressure-sensitive rubber alongside pentacene organic thin-fi lm transistor (OTFT) circuits. [ 3a ] In optical-sensor applications, Forrest et al. have shown an integrated OTFT-photodetector device with a sensitivity dynamic range of 12 bits for monochromatic light sensing at 580 nm. [ 5 ] Apart from pressure and light, heat is another important physical parameter that is often measured and thermal sensors have a lot of application potentials. High-sensitivity temperature sensors can be used for electronic skins, electronic health monitoring, and detecting patients’ body temperatures. However, unlike the pressure and optical sensors, OTFT-based temperature sensing devices with high sensitivity are yet to be demonstrated. As the glass transition temperatures of organic semiconductors are relatively low, the operating temperature of such organic temperature sensors is usually limited to around 100 ° C, making it extremely suitable for electronic skin or medical applications. Unfortunately the conductivity variation of the organic thin-fi lms in the resistor or diode structures between room temperature and 100 ° C is usually less than 10. [ 3b ] This results in limited sensitivity of the organic temperature sensors, especially in comparison with the silicon-based devices. [ 6 ]

Digital broadband linearization of optical links.

Abstract: We present a digital postprocessing linearization technique to efficiently suppress dynamic distortions added to a wideband signal in an analog optical link. Our technique achieves up to 35 dB suppression of intermodulation distortions over multiple octaves of signal bandwidth. In contrast to conventional linearization methods, it does not require excessive analog bandwidth for performing digital correction. This is made possible by regenerating undesired distortions from the captured output, and subtracting it from the distorted digitized signal. Moreover, we experimentally demonstrate a record spurious-free dynamic range of 120 dB·Hz2/3 over a 6 GHz electrical signal bandwidth. While our digital broadband linearization technique advances state-of-the-art optical links, it can also be applied to other nonlinear dynamic systems.

Wideband Receiver for a Three-Dimensional Ranging LADAR System

Abstract: A low-noise, high-gain, wide-linear-dynamic-range, wide-band receiver for a pulsed, direct, three-dimensional ranging LADAR system has been designed and implemented in a 0.13 μm CMOS technology. Specific design techniques, including gain control scheme to widen linear dynamic range, gain allocating between blocks and noise minimization to improve SNR, frequency response compensation to extend bandwidth and ensure system stability, and output voltage swing boosting, have been proposed to achieve challenging design goals with linear dynamic range of 1:1600, equivalent input-referred current noise of less than 5.6 pA/√Hz, high gain of 78 dBΩ, maximum output swing of at least 500 mV, bandwidth of at least 500 MHz, and low sensitivity to temperature variation over the range from -10°C to 60°C, in the presence of 2 pF photodiode parasitic capacitance.

Optical fiber strain sensor with extended dynamic range based on specklegrams

Abstract: In this paper, a processing scheme based on the morphological similarities of speckle patterns is proposed to extend the dynamic range of Fiber Specklegram Sensors (FSS). The method has been applied to a low cost FSS demonstrating its good performance to extend the dynamic range of strain measurements. The scheme analyzes the pattern energy distribution to establish the current modal state of the FSS and employs the correlation value with the reference modal state specklegram to determine the fine strain measurements. The achieved results exhibit a very high performance, making this low cost technology applicable to structural monitoring.

Dynamic range improvement of a microwave photonic link based on bi-directional use of a polarization modulator in a Sagnac loop.

Abstract: A novel microwave photonic link (MPL) with an improved spurious-free dynamic range (SFDR) based on a bidirectional use of a polarization modulator (PolM) in a Sagnac loop is proposed and demonstrated. The PolM in the loop functions, in conjunction with a polarization controller and a polarization beam combiner, as a Mach Zehnder modulator (MZM), which only modulates the incident light wave along the clockwise direction, leaving the counter-clockwise light wave unmodulated due to the velocity mismatch. Two clockwise intensity-modulated signals along two paths (Path 1 and Path 2) are generated, with one (Path 2) combined with the non-modulated light wave from the counter-clockwise direction to suppress part of the optical carrier. By controlling the power relationship between the two paths, the third-order intermodulation distortion (IMD3) can be fully suppressed, and thus an MPL with improved dynamic range is achieved. A theoretical analysis is presented, which is validated by an experiment. The IMD3 can be suppressed by 50 dB, giving an improvement in SFDR of 16 dB.

Tunable Class AB CMOS Gm-C Filter Based on Quasi-Floating Gate Techniques

Abstract: A tunable CMOS Gm-C channel-select low-pass filter is presented. Class AB operation overcomes the dynamic range versus static power tradeoff of conventional channel-select filter topologies. Programmable transconductors are designed using quasi-floating gate transistors, which provide class AB operation without requiring extra supply voltage or power requirements and keeping accurately set quiescent currents. The filter can be applied to channel selection in highly integrated, low power zero-IF wireless receivers. For example, its frequency tuning range and linearity makes it suitable for a dual-mode Bluetooth/ZigBee zero-IF receiver. Measurement results for a test chip prototype in a 0.5 μm standard CMOS process are presented, showing a THD <; -55 dB for an input of 1.2 Vpp, which corresponds to peak currents 300% larger than the bias current.

Wide dynamic range using monochromatic sensor

Abstract: The disclosure extends to methods, systems, and computer program products for widening dynamic range within an image in a light deficient environment.

A fully differential charge-balanced accelerometer for Electronic Stability Control

Abstract: An accelerometer for electronic stability control utilizes a two-mass mechanical sensor element to implement a fully-differential signal path, achieving robustness against electromagnetic interference (EMI) without the need for external shielding in the package. The EMI rejection is augmented further with a pseudo-random chopping scheme, which spreads the interference over a wide bandwidth, reducing its in-band portion to the level of the noise floor. The chopping function maintains zero-mean voltage waveforms across the sensor electrodes, which is also beneficial for the long-term offset stability of the device. A charge-balanced capacitance-to-voltage converter provides linear transduction for displacements of the proof-mass up to 70% of the gap and minimizes the residual electrostatic forces. A dual-axis design occupies 1.1 mm 2 in 0.18- μm CMOS and consumes 820 μA from an internally regulated 1.9-V supply. The system achieves 380 μg/ √Hz noise floor and 84-dB dynamic range. The offset variation in the automotive temperature range of -40 to +140°C has a 3 σ range of ±11 mg.

Parameter Automation in a Dynamic Range Compressor

Abstract: Dynamic range compression is a nonlinear, time dependent audio effect. As such, preferred parameter settings are difficult to achieve even when there is advance knowledge of the input signal and the desired perceptual characteristics of the output. We introduce an automated approach to dynamic range compression where the parameters are configured automatically based on real-time, side-chain feature extraction from the input signal. Parameters are all dynamically varied depending on extracted features, leaving only the threshold as a user controlled parameter to set the preferred amount of compression. We analyze a series of automation techniques, including comparison of methods based on different signal characteristics. Subjective evaluation was performed with amateur and professional sound engineers, which established preference for dynamic range compressor parameters when applied to musical signals, and allowed us to compare performance of our various approaches against manual parameter settings.

Context based inverse mapping method for layered codec

Abstract: Context based inverse mapping methods are provided. An image with pixel values within a lower dynamic range can be mapped to an image with pixel values within a higher dynamic range by utilizing context information associated with pixels in the lower dynamic range image.

217 km long distance photon-counting optical time-domain reflectometry based on ultra-low noise up-conversion single photon detector

Abstract: We demonstrate a photon-counting optical time-domain reflectometry with 42.19 dB dynamic range using an ultra-low noise up-conversion single photon detector. By employing the long-wave pump technique and a volume Bragg grating, we achieve a noise equivalent power of -139.7 dBm/√Hz for our detector. We perform the OTDR experiments using a fiber of length approximate 217 km, and show that our system can identify defects along the entire fiber length in a measurement time of 13 minutes.

Fast Co-Polar and Cross-Polar 3D Pattern Synthesis With Dynamic Range Ratio Reduction for Conformal Antenna Arrays

Abstract: This paper presents a fast method for conformal antenna arrays that enables the synthesis of 3D co-polar and cross-polar patterns, simultaneously reducing the dynamic range ratio (DRR) of the array excitations. The power synthesis problem is reduced to a field synthesis one by introducing two auxiliary phase patterns: one for the co-polar pattern and the other for the cross-polar pattern. The problem is then iteratively solved with respect to the two auxiliary phase patterns and to the array excitations. A modified version of the method is also proposed, for the particular case where the DRR reduction is not required, obtaining a further strong reduction of the computational time.

Performance of an LPD prototype detector at MHz frame rates under Synchrotron and FEL radiation

Abstract: A MHz frame rate X-ray area detector (LPD - Large Pixel Detector) is under development by the Rutherford Appleton Laboratory for the European XFEL. The detector will have 1 million pixels and allows analogue storage of 512 images taken at 4.5 MHz in the detector front end. The LPD detector has 500 mm thick silicon sensor tiles that are bump bonded to a readout ASIC. The ASICs preamplifier provides relatively low noise at high speed which results in a high dynamic range of 10^5 photons over an energy range of 5-20 keV. Small scale prototypes of 32x256 pixels (LPD 2-Tile detector) and 256x256 pixels (LPD supermodule detector) are now available for X-ray tests. The performance of prototypes of the detector is reported for first tests under synchrotron radiation (PETRA III at DESY) and Free-Electron-Laser radiation (LCLS at SLAC). The initial performance of the detector in terms of signal range and noise, radiation hardness and spatial and temporal response are reported. The main result is that the 4.5 MHz sampling detection chain is reliably working, including the analogue on-chip memory concept. The detector is at least radiation hard up to 5 MGy at 12 keV. In addition the multiple gain concept has been demonstrated over a dynamic range to 10^4 at 12 keV with a readout noise equivalent to <1 photon rms in its most sensitive mode.

A low-noise time-gated single-photon detector in a HV-CMOS technology for triggered imaging

Abstract: An optical imager for triggered applications is presented. The detector consists of a 10 × 43 array of single-photon avalanche pixels and exhibits an unusual fill-factor of 67%. It has been fabricated in a conventional 0.35 μm HV-CMOS process. The array presents an average dark count rate of 67 kHz at a reverse bias overvoltage of 1 V. Due to the large sensor area of 20 μm × 100 μm, the array is operated in a time-gated mode to reduce the probability of detecting the sensor noise down to 10 −4 noise counts per frame with an active period of 4 ns. The crosstalk can be minimized to negligible levels also by means of the time-gated operation. A number of experiments have been conducted on the detector to show that the proposed technique is advantageous in improving the imager signal-to-noise ratio, dynamic range, contrast and spatial resolution.

All-digital signal-processing open-loop fiber-optic gyroscope with enlarged dynamic range.

Abstract: We propose and realize a new open-loop fiber-optic gyroscope (FOG) with an all-digital signal-processing (DSP) system where an all-digital phase-locked loop is employed for digital demodulation to eliminate the variation of the source intensity and suppress the bias drift. A Sagnac phase-shift tracking method is proposed to enlarge the dynamic range, and, with its aid, a new open-loop FOG, which can achieve a large dynamic range and high sensitivity at the same time, is realized. The experimental results show that compared with the conventional open-loop FOG with the same fiber coil and optical devices, the proposed FOG reduces the bias instability from 0.259 to 0.018 deg/h, and the angle random walk from 0.031 to 0.006 deg/h1/2, moreover, enlarges the dynamic range to ±360 deg/s, exceeding the maximum dynamic range ±63 deg/s of the conventional open-loop FOG.

A Broadband Logarithmic Power Detector in 0.13- $\mu$ m CMOS

Abstract: A broadband logarithmic (log) power detector with a wide dynamic range has been developed using a 0.13 μm CMOS process. The proposed power detector consists of three signal amplification and rectification branches combined in parallel for broadband operation. The required linearity and dynamic range are provided by high-linearity rectifier design using active degeneration technique. The fabricated power detector chip has a size of 1.0 mm × 0.75 mm and consumes 35.2 mW. The power detector shows a dynamic range wider than 43 dB with ± 1 dB log error up to 14 GHz. Over 50 dB dynamic range is achieved at 16 GHz with a slightly higher log error of ± 1.5 dB.

High Dynamic Range Imaging: Sensors and Architectures

Abstract: Illumination is a crucial element in many applications, matching the luminance of the scene with the operational range of a camera. When luminance cannot be adequately controlled, a high dynamic range (HDR) imaging system may be necessary. These systems are being increasingly used in automotive on-board systems, road traffic monitoring, and other industrial, security, and military applications. This book provides readers with an intermediate discussion of HDR image sensors and techniques for industrial and non-industrial applications. It describes various sensor and pixel architectures capable of achieving HDR imaging, as well as software approaches to make high dynamic range images out of lower dynamic range sensors or image sets. Some methods for automatic control of exposure and dynamic range of image sensors are also introduced.

Wavelength-multiplexing phase-sensitive surface plasmon imaging sensor.

Abstract: A wavelength-multiplexing phase-sensitive surface plasmon resonance (SPR) imaging sensor offering wide dynamic detection range and microarray capability is reported. Phase detection is accomplished by performing self-interference between the s- and p- polarizations within the signal beam. A liquid crystal tunable filter is used to sequentially select the SPR excitation wavelength from a white light source. This wavelength-multiplexing approach enables fast detection of the sensor’s SPR phase response over a wide range of wavelengths, thereby covering literally any regions of interest within the SPR dip and thus maintaining the highest sensitivity point at all times. The phase-sensitive approach is particularly important for imaging SPR sensing applications because of its less stringent requirements for intensity signal-to-noise ratio, which also means the possibility of using uncooled modest resolution analog-to-digital conversion imaging devices. Experimental results demonstrate a resolution of 2.7×10−7 RIU with a dynamic range of 0.0138 RIU.

Continuous-Wave THz Homodyne Spectroscopy and Imaging System With Electro-Optical Phase Modulation for High Dynamic Range

Abstract: We present a terahertz (THz) continuous-wave coherent homodyne spectroscopy and imaging system based on THz phase control using electrooptic (EO) phase modulation for fast measurement without mechanical delay movement. After describing the degradation effects of detection signal by the optical laser noise and parasitic amplitude modulation, we propose the push-pull EO phase modulation with optical delay control for dynamic range enhancement. Using wideband unitraveling-carrier photodiode and InGaAs photoconductive antenna, spectroscopy up to a 1.5-THz frequency range and imaging are demonstrated.

A 0.5 V PWM CMOS Imager With 82 dB Dynamic Range and 0.055% Fixed-Pattern-Noise

Abstract: This paper presents a 0.5 V operated pulse-width modulation (PWM) CMOS imager with threshold-variation canceling (TVC) and programmable current-controlled threshold (PCCT) schemes implemented in 0.18 μm CMOS technology. The proposed TVC scheme efficiently improves the fixed-pattern-noise (FPN) issue caused by process variation in conventional PWM sensors. The limited dynamic range in ultra-low-voltage operated sensor can be extended by 56.5 dB with the proposed PCCT operation. The measurement results of the prototype chip show an array FPN of 0.055%, a column FPN of 0.016%, a dark random noise of 0.65 LSB, and a dynamic range (DR)of 82 dB. The total chip consumes 4.95 uW and 29.6 μW at 11.8 fps and 78.5 fps, which achieves an iFOM of 163.9 pW/f-p and 147.3 pW/f-p, respectively.

Image capture apparatus, method of controlling image capture apparatus, and electronic device

Abstract: An image capture apparatus is provided that is capable of accurately determining exposure conditions of multiple images to be used in high dynamic range compositing in a short duration, based on a captured image. A scene dynamic range is computed based on luminance information obtained from an image captured with a standard exposure according to a luminance zone to be prioritized in high dynamic range shooting and luminance information obtained from an image captured with an over-exposure or an under-exposure relative to the standard exposure. An exposure range of multiple images for creating a high dynamic range image is determined according to the computed dynamic range.

Brightness Control in Dynamic Range Constrained Visible Light OFDM Systems

Abstract: Visible light communication (VLC) systems can provide illumination and communication simultaneously via light emitting diodes (LEDs). Orthogonal frequency division multiplexing (OFDM) waveforms transmitted in a VLC system will have high peak-to-average power ratios (PAPRs). Since the transmitting LED is dynamic-range limited, OFDM signal has to be scaled and biased to avoid nonlinear distortion. Brightness control is an essential feature for the illumination function. In this paper, we will analyze the performance of dynamic range constrained visible light OFDM systems with biasing adjustment and pulse width modulation (PWM) methods. We will investigate the trade-off between duty cycle and forward ratio of PWM and find the optimum forward ratio to maximize the achievable ergodic rates.

Calibrating image plate sensitivity in the 700 to 5000 eV spectral energy range

Abstract: This paper describes a method to calibrate image plate sensitivity for use in the low energy spectral range. Image plates, also known as photostimulable luminescence (PSL) detectors, have often proved to be a valuable tool as a detector for plasma physics studies. Their advantages of large dynamic range, high stopping power, and resistance to neutron damage sometimes outweigh the problems of limited resolution and the remote processing required. The neutron damage resistance is required when the X-ray source is producing a high neutron flux. The Static X-ray Imager (SXI) is a key diagnostic on the National Ignition Facility (NIF) target chamber at LLNL for use in determining the symmetry of the laser beams. The SXI is essential to proper interpretation of the data from the Dante diagnostic to determine the X-ray radiation temperature. It is comprised of two diagnostics located at the top and the bottom of the target chamber. The usual detector is a large array CCD camera. For shots giving high yields of neutrons, the camera would not only be blinded by the neutrons, it would be damaged. To get around this problem, an image plate (IP) is used as the detector. The NIF application covers the energy range from 700 to 5000 eV. The type of image plates typically used for plasma physics are the Fuji BAS-MS, BAS-SR, and BAS-TR models. All models consist of an X-ray sensitive material made of BaF(Br,I):Eu 2+ embedded in a plastic binder. X-rays incident on the phosphor ionize the Eu 2+ producing Eu 3+ and free electrons that are trapped in lattice defects (F-centers) produced by the absence of halogen ions in the BaF 2 crystal. An image plate readout scanner irradiates the IP with a red laser causing reduction of the Eu 3+ and emission of a blue photon. The photon is collected using a photomultiplier and digitized to make an electronic image. Image plates are cleared of all F-centers by putting them under a bright light for about 10 minutes. They are then ready for producing a new X-ray image. The MS IP model has the higher sensitivity and the SR IP and TR IP models are designed for higher resolution. The MS and SR IPs have a thin Mylar coating that protects the sensitive layer. The TR model has no protective layer and is more sensitive at the lower X-ray energies but must be handled more carefully. The raw image data from the Fuji scanner can be converted to units of PSL that are proportional to the photon count. The equation relating PSL to the raw greyscale value is: PSL = (R/100) 2 (4000/S)exp 10 {L(G/(2 B -1)-1/2)} where R is the resolution in μm S is the sensitivity setting L is the latitude B is the dynamic range (8 or 16 bits) G is the raw image greyscale value. The IP photon sensitivity is defined as the PSL output per photon input and is a function of the photon energy. Meadowcroft et al in 2008 published the sensitivity for the three types of image plates in the spectral range from 1 to 100 keV. Maddox et al measured the sensitivity for type MS and SR image plates from 8 to 80 keV using the NSTec High Energy X-ray (HEX) source, a fluorescer type X-ray source. The Meadowcroft and Maddox measurements used similar X-ray sources for the higher spectral and the same type of IP scanner, the FLA 7000. There is reasonable agreement between the Maddox and Meadowcroft sensitivity measurements of MS and SR type IP for the at spectral energies above 20 keV, but the Maddox sensitivities are much lower than those of Meadowcroft in the energy range below 20 keV. Recently Bonnet et al published a model for the photon sensitivity based upon the amount of energy deposited and Monte Carlo calculations to incorporate the specifics of the X-ray absorption and the readout process. The model was calibrated for sensitivity using radioactive sources. The model was compared to the previous publications cited. The Bonnet model tends to agree with the Meadocroft measurements at the low spectral energies. The present paper describes the measurement of IP sensitivity in the spectral range from 700 to 8000 eV. The sensitivity in this spectral range had not previously been measured and was needed for the NIF application. A calibration at the low energy range was done using a diode source and a band pass filter. X-ray beam is filtered and limited by the applied voltage to provide a spectral band that is about 1/10 of the average spectral energy. The X-ray flux is measured using a photodiode that is traceable to National Institute for Standards and Technology (NIST). The spectrum for each X-ray band is measured using a silicon drifted detector. The photodiode calibration method is described. Measurements were made on SR, TR, and specially coated TR image plates. The measurement results will be presented and the uncertainties in the measurement will be discussed. The results will be compared to other measurements and estimation methods.

CMOS X-Ray Detector With Column-Parallel 14.3-bit Extended-Counting ADCs

Abstract: This paper presents a CMOS X-ray detector with 14.3-bit column-parallel extended-counting analog-to-digital converters (EC-ADCs). The CMOS X-ray detector employs column-parallel EC-ADCs with a built-in analog binning function for high gray-scale resolution and small silicon area. The total area of the 14.3-bit EC-ADC and digital logic circuits is only 100 μm × 1100 μm. The ΔΣ modulator in the EC-ADC simultaneously performs the upper 3-bit conversion and the analog binning operation. To reduce the fixed-pattern noise (FPN) from the ADC and the pixel, we adopt the digital correlated-double sampling technique. A bias circuit for the column-parallel readout architecture in a large-area CMOS X-ray detector is proposed to improve the uniformity among column ADCs. Simulation results show that the uniformity of output voltages among column ADCs is improved to 50 times the uniformity in the conventional bias circuit. The proposed CMOS X-ray detector has been fabricated using a 0.35-μm CMOS process. The measured differential column FPN and random noise without X-ray exposure at the frame rate of 60 frames/s are 3.10 and 5.17 least significant bit, respectively. The measured dynamic range is 68.3 dB under the same conditions.