Digital Pixel Research Articles

Edge Detection and Accurate Rectification Technology in the Digital Detection for Dry Cell Substratum Pixel

The development of dry cell production in the world is advancing towards the high-speed and intellectualization direction, the input reduction for production cost by improving the comprehensive performance level and utilizing the advanced equipment has been the urgent demand for development of battery industry. The lagging situation that the detection by naked eye manually is relied to perform the quality assurance for dry cell substratum is broken based on the online high-speed automatic detection technology for pixel digitization of visual image. The principles on battery image processing and feature division as well as the principle on pixel over- fitting and accurate rectification during the process of pixel digitization detection for dry cell substratum are discussed in this paper, and such base and core for battery image processing as edge detection and accurate rectification technology are described.

Application of dynamic counter circuits in programmable digital pixel sensor architectures

ABSTRACTIn this paper, a high dynamic range digital pixel sensor (DPS) is presented. Each pixel receives light illumination and converts the intensity level to a digital code. The analog‐to‐digital conversion is performed in‐pixel. The pixel structure incorporates light to pulse signal converter and compact in‐pixel dynamic counter to convert the pulse signal to binary coded data. Different variations of the custom design dynamic counters are analyzed in a 0.18 µm technology, and their application in the DPS is investigated. It is shown that due to the limited clock frequency required in the sensor pixel, the dynamic counter can be incorporated as a pulse to binary code converter. Performance specifications such as power consumption, dynamic range and resolution of the presented structure are investigated using a 100 × 100 pixel sensor. The presented sensor is an effective solution for use in digital field programmable smart image sensors and vision chips since the pixel output is a regular binary code while no global digital counter bus is required. The fill factor of the presented design remains close to that of typical DPSs. Copyright © 2013 John Wiley & Sons, Ltd.

Readout Integrated Circuits with Pixel-Level ADC for Ultraviolet FPA Applications

An array of 128×128 digital pixel sensors (DPS) that performs both in pixel light current integration and analog-to-digital conversion is presented. The pixel fabricated on a DP4M CMOS process provides a digital output of ultraviolet light intensity via an integrated multiple-channel bit-serial (MCBS) ADC. Due to low light current (~pA) of ultraviolet focal-plane-array, the architecture of capacitive trans-impedance amplifier (CTIA) is used. The proposed readout integrated circuits have a 12-bit resolution, 70dB dynamic range and 99% of linearity.

A New Chaotic Image Scrambling Scheme Based on Spatial Bit-Level Map

Image scrambling is an important technique in digital image encryption and digital image watermarking. This paper proposes a new image scrambling algorithm based on chaotic sequence and spatial bit-level map. First, I used Logistic chaotic sequences to rearrange digital image pixels into one-dimensional (1-D) sequence, then the value of each pixel in the sequence was decomposed into k-bits which constituted a two-dimensional (2-D) bit matrix. Second, the spatial bit-level map was performed in the 2-D bit matrix to generate pixels with new values. Finally, the scrambling image was generated according to these pixels. This algorithm can scramble image based on the pixel’s position and the value and their corresponding probability. The experimental results show that this scrambling algorithm possesses perfect confusion properties and it can resist various attacks. Also it can apply to non-square image.

Solar thematic maps for space weather operations

Thematic maps are arrays of labels, or “themes,” associated with discrete locations in space and time. Borrowing heavily from the terrestrial remote sensing discipline, a numerical technique based on Bayes' theorem captures operational expertise in the form of trained theme statistics, then uses this to automatically assign labels to solar image pixels. Ultimately, regular thematic maps of the solar corona will be generated from high‐cadence, high‐resolution SUVI images, the solar ultraviolet imager slated to fly on NOAA's next‐generation GOES‐R series of satellites starting ∼2016. These thematic maps will not only provide quicker, more consistent synoptic views of the sun for space weather forecasters, but digital thematic pixel masks (e.g., coronal hole, active region, flare, etc.), necessary for a new generation of operational solar data products, will be generated. This paper presents the mathematical underpinnings of our thematic mapper, as well as some practical algorithmic considerations. Then, using images from the Solar Dynamics Observatory (SDO) Advanced Imaging Array (AIA) as test data, it presents results from validation experiments designed to ascertain the robustness of the technique with respect to differing expert opinions and changing solar conditions.

The Endothelial Safety of Using a Gentian Violet Dry-Ink “S” Stamp for Precut Corneal Tissue

To determine the endothelium damage resulting from the application of "dry" gentian violet (GV) stromal markings on corneas precut for Descemet stripping automated endothelial keratoplasty (DSAEK) using a Moria "S" Stamp. Five precut corneas had the stromal graft bed marked with GV using the Moria "S" stamp and 6 precut corneas were left unmarked as controls. After applying the ink to the stamp, care was taken to allow the alcohol carrier to dry for 10 seconds before applying the dry dye to the stromal surface. Tissue was then trephinated and stained with calcein AM to assess endothelial viability. Grafts were photographed and digital pixel planometry, using an established analysis technique, was used to compare the damage between the control and experimental groups. The mean percent cell damage of corneas treated with GV "S" stamp (n = 5) was 8.6% (range 4.4-12.9), and it was 8.1% (range 3.9-15.1) in the DSAEK control set (n = 6). Median percent cell damage was 6.7% among GV-treated corneas and 7.4% among control corneas. The distributions were not significantly different between groups (Mann-Whitney U test = 15.0, two-tailed P = 1.0). Moreover, no "S" pattern of damage was seen in any study eye. There were no significant differences in endothelial damage between the 2 groups. GV stromal markings may be applied without undue damage to the endothelium using the dry-ink technique described.

Neuroanimatics: Hyperrealism and digital animation’s accidental mark

Digital animation is arguably a medium that can produce any image that the human brain can imagine, but is this all that it can do? It is not without good reason that animation has become a popular and enduring medium: animators and artists have long known that certain forms of simplification and exaggeration are more pleasing than others. This article will argue that animation has the ability to not only match the human imagination, but also to improve on it via the mark-making process itself, or more accurately via the ‘accidental’ mark-making process. Utilizing discoveries in neuroscience and neuroaesthetics I will examine the effects of this ‘accidental’ mark on both traditional and digital animation production and spectatorship. I will establish that there are intrinsic qualities in the digital pixel that render the digital animation medium truly unique in terms of its representational qualities. However, this unique ability does not lie, as might be expected, in the area of digital realism, but rather in the domain of the hyperreal.

Optimal scan strategy for mega-pixel and kilo-gray-level OLED-on-silicon microdisplay

The digital pixel driving scheme makes the organic light-emitting diode (OLED) microdisplays more immune to the pixel luminance variations and simplifies the circuit architecture and design flow compared to the analog pixel driving scheme. Additionally, it is easily applied in full digital systems. However, the data bottleneck becomes a notable problem as the number of pixels and gray levels grow dramatically. This paper will discuss the digital driving ability to achieve kilogray-levels for megapixel displays. The optimal scan strategy is proposed for creating ultra high gray levels and increasing light efficiency and contrast ratio. Two correction schemes are discussed to improve the gray level linearity. A 1280×1024×3 OLED-on-silicon microdisplay, with 4096 gray levels, is designed based on the optimal scan strategy. The circuit driver is integrated in the silicon backplane chip in the 0.35 μm 3.3 V-6 V dual voltage one polysilicon layer, four metal layers (1P4M) complementary metal-oxide semiconductor (CMOS) process with custom top metal. The design aspects of the optimal scan controller are also discussed. The test results show the gray level linearity of the correction schemes for the optimal scan strategy is acceptable by the human eye.

A Monitor Calibration Model Based on Artificial Neural Network

There is a very complicated nonlinear relationship between the input digital image pixel value and the display colors, which is difficult to be described by traditional linear methods to achieve high accuracy. In the study, a monitor calibration model is established based on artificial BP neural network theory and by the hue angle range of the experimental data display classification. Because of the good simulation of nonlinear properties of the BP neural network, the calibration model achieves high accuracy. The color error mean value between the chroma value to be displayed and the chroma value driven by the image pixel value which is calculated by the calibration model is rather less than that of the minimum range of the human eye can identify. The calibration model could be used in the gamut matching phrase in the printing color management system, when the monitor is severed as an output device.

SU-E-T-69: A Novel Method Using Agfa-Kodak- Computer Radiography System for Routine Quality Assurance Tests on Linear Accelerators

Purpose: Since conventional radiographic films are becoming obsolete, we have developed a novel technique utilizing Computer Radiography (CR) plates to perform routine Linac quality assurance checks. Methods: A photostimulable CR plate can detect both direct and indirect ionization radiation, and is even sensitive to photons in the visible range. A technique involving optical bleaching of radiation field on CR plate is being established as the calibration tool for performing routine quality checks such as: light field radiation congruence, symmetric/asymmetric jaw positioning. The CR plate is removed from its cassette with minimal background light and is exposed to a known field size of 6/18 MV photons in air at a fixedsource to surface distance. The jaws are then moved in to form a smaller field size, and light field is then shone on the pre exposed plate. This causes photo bleaching of radiation field proportional to the jaw settings and thereby providing a suitable surrogate to establish the light and radiation coincidence. The plate is then read utilizing a Kodak (ACR 2000i) scanner which reads the photo stimulated luminescence and converts the signal into a digital image pixel map. Analysis using a MATLAB-based algorithm was done to compute the dose gradient at the junction of the light and radiation field. The technique has been tested against conventional methods of usingfilm and graph paper. Results: All light and radiation field measurements using the CR plate were within 1 mm from measurements. The method has been verified for its reproducibility and estimated uncertainty involving software based analysis has been found to be within +/− 0.2%. Conclusions: A method to efficiently, accurately and reproducibly perform routine QA has been developed. The technique has yielded a reproducible method to quantify the congruence between the light and the radiation field.

TU‐A‐BRB‐08: A Technique to Determine the Gantry Laser and the Proton Pencil Beam Coincidence Using Computer Radiography Detector for Routine Quality Checks

Purpose: A computed radiography (CR) detector with photostimulable phosphors can detect both direct and indirect ionization radiation, and is even sensitive to photons in the visible range. The purpose of this work is to develop and validate a technique using CR to check both proton radiation versus localization laser coincidence and spot positioning accuracy for magnetically scanned proton pencil beam spots (PPBS). Methods: CR plate is removed from its cassette and set up perpendicular to the incident beam and exposed to an array of PPBS irradiated at predefined coordinates. Upon exposure of the particle radiation, the CR detector is then exposed to the gantry's laser systems. The plate is then put through a digital scanner which then reads the photo stimulated luminescence and converts the signal into a digital image pixel map. MATLAB®‐based analysis software and ImageJ® image processing tools were used to compute the dose gradient from the laser bleaching of the proton exposure of the detector and for quantification of the results of this QA check procedure. The technique further allows quantitative determination of both spot positions, and the relationship between X ray system used for image guided patient setup and the PPBS delivery. Results: Both the coincidence between laser representing the gantry isocenter and center of PPBS along the central axis and spot positions can be checked within 1mm accuracy with the CR detector. Conclusions: We have demonstrated that our technique allows determining the coincidence between the laser and radiation beam. The technique described here is found to be suitable for periodic QA checks of relative positions of the spot center relative to the gantry isocenter and beam central axis. Improvements of this technique by considering the effect of detector's quantum yield and modulation transfer function on the data remain subject of further study.

Applications of Near Sets

Near sets are disjoint sets that resemble each other. Resemblance is determined by considering set descriptions defined by feature vectors (n-dimensional vectors of numerical features that represent characteristics of objects such as digital image pixels). Near sets are useful in solving problems based on human perception [44, 76, 49, 51, 56] that arise in areas such as image analysis [52, 14, 41, 48, 17, 18], image processing [41], face recognition [13], ethology [63], as well as engineering and science problems [53, 63, 44, 19, 17, 18]. As an illustration of the degree of nearness between two sets, consider an example of the Henry color model for varying degrees of nearness between sets [17, §4.3]. The two pairs of ovals in Figures 1 and 2 contain colored segments. Each segment in the figures corresponds to an equivalence class where all pixels in the class have matching descriptions, i.e., pixels with matching colors. Thus, the ovals in Figure 1 are closer (more near) to each other in terms of their descriptions than the ovals in Figure 2. It is the purpose of this article to give a bird’s-eye view of recent developments in the study of the nearness of sets.

A Quantum-Limited Highly Linear Monolithic CMOS Detector for Computed Tomography

Computed tomography (CT) detector requires quantizing the wide dynamic range (WDR) photocurrent with high speed. Existing CMOS CT detectors are limited by their low linearity. They also need high-resolution external analog-to-digital converters (ADC) to quantize the WDR. In this work, a novel synchronous partial quantization technique is developed to enable monolithic CMOS CT pixel detector. Improved from previous current quantization designs, the new pixel detector quantizes the photocurrent in the charge domain with constant charge packet size. As the result, the pixel detector can quantize the WDR photocurrent with improved linearity. The two-step charge-domain ADC scheme also allows low resolution single-slope ADCs for residual voltage quantization, which enables in-pixel integration. A prototype pixel detector is fabricated in a 0.35 μm CMOS process. Silicon measurements show the detector can quantize signal currents from 6 pA to 63.4 nA with relative gain deviation lower than 0.06% at 1.1 kHz frame rate, which does not generate detector-induced artifact after the image reconstruction. The detector noise is smaller than the X-ray Poisson noise in the whole signal range. The minimum detector noise is 0.8 pArms. Hence, the detector achieves 16.6 bits dynamic range. The geometrical detective efficiency (GDE) of the detector is 75.5% including the band-gap voltage reference and ADC. The digital pixel detector can be easily tiled into a 2-D CT detection panel.

A Printer Point Set Gamut Model Based on BP Neural Network

In the color management system, device gamut is an important prerequisite for effective color management. Currently, device gamut is described by convex hull model. In this method, electronic standard color card is output on certain media, the chromatic values of the color blocks of the color card are measured as vertices to build the three-dimensional space of convex hull. In spite of the simplicity of the description method in manipulation, the factors that can't be ignored are as the following, the relatively representative of the color blocks on the color card and the device gamut has something to do with the factors such as device feature, as well as the surrounding light and device parameters. Near the edge of the convex hull, the device limit color points perhaps locate inside and outside the edge of the convex hull, so the convex hull model can't describe the device gamut exactly. In the research, based on mapping relation of digital image pixel value and its corresponding printed color, printer characterization model is established based on BP neural network with exactitude to a perfect certainty. Then, digital image pixel values with kinds of intervals are taken to calculate the color point sets by the printer characterization model, and the device gamut could be described by the color points sets. By visual method, both the convex hull model and the point set model are compared. The experiment shows that the point set models describe the printer gamut more precise than the convex hull model.

Noise in a CMOS digital pixel sensor

Based on the study of noise performance in CMOS digital pixel sensor (DPS), a mathematical model of noise is established with the pulse-width-modulation (PWM) principle. Compared with traditional CMOS image sensors, the integration time is different and A/D conversion is implemented in each PWM DPS pixel. Then, the quantitative calculating formula of system noise is derived. It is found that dark current shot noise is the dominant noise source in low light region while photodiode shot noise becomes significantly important in the bright region. In this model, photodiode shot noise does not vary with luminance, but dark current shot noise does. According to increasing photodiode capacitance and the comparator's reference voltage or optimizing the mismatch in the comparator, the total noise can be reduced. These results serve as a guideline for the design of PWM DPS.

A 70-$\mu$m Pitch 8-$\mu$W Self-Biased Charge-Integration Active Pixel for Digital Mammography

This paper presents a new low-power compact CMOS active pixel circuit specifically optimized for full-field digital mammography. The proposed digital pixel sensor (DPS) architecture includes self-bias capability at ±10% accuracy, up to 15 nA of dark-current autocalibration, built-in test mechanisms, selectable e(-)/h(+) collection, 10-b lossless charge-integration analog-to-digital conversion, more than 1 decade of individual gain tuning for fixed pattern noise cancellation, and a 50-Mb/s digital-only input/output interface. Experimental results for a 70-μm pitch 8-μW DPS cell example are reported in 0.18-μm CMOS 1-polySi 6-metal technology.

Quadrant-Based Online Spatial and Temporal Compressive Acquisition for CMOS Image Sensor

The concept of compressive acquisition image sensor is to compress data while sensing and prior to storage. In this paper, the concept of compressive acquisition image sensor is developed, implemented and experimentally validated for both spatial and temporal domains. In the proposed scheme, the image sensor array is divided into quadrants integrating logic circuitry which performs online spatial compression of the raw data prior to storage. The quadrants are subsequently further classified into background/non-background quadrants by an off-array judge logic which enables to adaptively track the associated temporal information. Temporal redundancy between frames is hence removed in the readout phase. The proposed compressive acquisition algorithm is simulated and experimentally validated for both spatial and temporal domains through a hardware prototype. Experimental results show that the proposed algorithm enables more than 50% memory saving at a PSNR level of 26 dB with around 0.5 BPP. This result not only greatly reduces the memory requirements for a digital pixel CMOS image sensor, but also results in area saving as data is only stored after being compressed.

Digital time‐modulation pixel memory circuit in LTPS technology

Abstract— A digital time‐modulation pixel memory circuit on glass substrate has been designed and verified for a 3‐μm low‐temperature polysilicon (LTPS) technology. From the experimental results, the proposed circuit can generate 4‐bit digital codes and the corresponding inversion data with a time‐modulation technique. While the liquid‐crystal‐display (LCD) panel operates in the still mode, which means the same image is displayed on the panel, a data driver for an LCD panel is not required to provide the image data of the frame by the proposed pixel memory circuit. This pixel memory circuit can store the frame data and generate its corresponding inversion data to refresh a static image without activating the data driver circuit. Therefore, the power consumption of a data driver can be reduced in the LCD panel.

P‐49: Design of Digital Time‐Modulation Pixel Memory Circuit on Glass Substrate for Low Power Application

AbstractA digital time‐modulation pixel memory circuit on glass substrate has been designed and verified in a 3‐μm low temperature poly‐silicon (LTPS) technology. The proposed circuit can generate 4‐bit digital codes and the corresponding inversion data by time‐modulation technique to refresh the static image without activating the data driver circuit. Therefore, the data driver of liquid crystal display (LCD) panel is not required to provide the image data of the frame by the proposed circuit while the LCD panel operates in the still mode. The power consumption from data driver can be further reduced in the LCD panel.

A CMOS Image Sensor With On-Chip Image Compression Based on Predictive Boundary Adaptation and Memoryless QTD Algorithm

This paper presents the architecture, algorithm, and VLSI hardware of image acquisition, storage, and compression on a single-chip CMOS image sensor. The image array is based on time domain digital pixel sensor technology equipped with nondestructive storage capability using 8-bit Static-RAM device embedded at the pixel level. The pixel-level memory is used to store the uncompressed illumination data during the integration mode as well as the compressed illumination data obtained after the compression stage. An adaptive quantization scheme based on fast boundary adaptation rule (FBAR) and differential pulse code modulation (DPCM) procedure followed by an online, least storage quadrant tree decomposition (QTD) processing is proposed enabling a robust and compact image compression processor. A prototype chip including 64×64 pixels, read-out and control circuitry as well as an on-chip compression processor was implemented in 0.35 μm CMOS technology with a silicon area of 3.2×3.0 mm2 and an overall power of 17 mW. Simulation and measurements results show compression figures corresponding to 0.6-1 bit-per-pixel (BPP), while maintaining reasonable peak signal-to-noise ratio levels.