Active Pixel Sensors: Are CCD's Dinosaurs?
12 Jul 1993-Vol. 1900, pp 2-14
TL;DR: ActivePixel Sensor (APS) as mentioned in this paper is a detector array technology that has at least one active transistor within the pixel unit cell, which eliminates the need for nearly perfect charge transfer, which makes CCD's radiation'soft' and difficult to use under low light conditions, difficult to integrate with on-chip electronics, difficulty to use at low temperatures, and difficulty to manufacture in non-silicon materials that extend wavelength response.
Abstract: Charge-coupled devices (CCDs) are presently the technology of choice for most imaging applications. In the 23 years since their invention in 1970, they have evolved to a sophisticated level of performance. However, as with all technologies, we can be certain that they will be supplanted someday. In this paper, the Active Pixel Sensor (APS) technology is explored as a possible successor to the CCD. An active pixel is defined as a detector array technology that has at least one active transistor within the pixel unit cell. The APS eliminates the need for nearly perfect charge transfer--the Achilles' heel of CCDs. This perfect charge transfer makes CCD's radiation 'soft,' difficult to use under low light conditions, difficult to manufacture in large array sizes, difficult to integrate with on-chip electronics, difficult to use at low temperatures, difficult to use at high frame rates, and difficult to manufacture in non-silicon materials that extend wavelength response. With the active pixel, the signal is driven from the pixel over metallic wires rather than being physically transported in the semiconductor. This paper makes a case for the development of APS technology. The state of the art is reviewed and the application of APS technology to future space-based scientific sensor systems is addressed.
Citations
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Abstract: The discomfort of internal gastrointestinal examination may soon be a thing of the past. We have developed a new type of endoscopy, which for the first time allows painless endoscopic imaging of the whole of the small bowel. This procedure involves a wireless capsule endoscope and we describe here its successful testing in humans.
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TL;DR: In this article, the requirements for CMOS image sensors and their historical development, CMOS devices and circuits for pixels, analog signal chain, and on-chip analog-to-digital conversion are reviewed and discussed.
Abstract: CMOS active pixel sensors (APS) have performance competitive with charge-coupled device (CCD) technology, and offer advantages in on-chip functionality, system power reduction, cost, and miniaturization. This paper discusses the requirements for CMOS image sensors and their historical development, CMOS devices and circuits for pixels, analog signal chain, and on-chip analog-to-digital conversion are reviewed and discussed.
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TL;DR: In this article, the performance of infrared thermal detectors as compared to photon detectors is investigated and an overview of focal plane array architecture is given with emphasis on monolithic and hybrid structures.
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Cites methods from "Active Pixel Sensors: Are CCD's Din..."
...Passive and active pixel sensors CMOS-based imagers for both IR and visible applications use active or passive pixels [46–50] as shown, in simplified form, in Fig....
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TL;DR: This article provides a basic introduction to CMOS image-sensor technology, design and performance limits and presents recent developments and future research directions enabled by pixel-level processing, which promise to further improveCMOS image sensor performance and broaden their applicability beyond current markets.
Abstract: In this article, we provide a basic introduction to CMOS image-sensor technology, design and performance limits and present recent developments and future directions in this area. We also discuss image-sensor operation and describe the most popular CMOS image-sensor architectures. We note the main non-idealities that limit CMOS image sensor performance, and specify several key performance measures. One of the most important advantages of CMOS image sensors over CCDs is the ability to integrate sensing with analog and digital processing down to the pixel level. Finally, we focus on recent developments and future research directions that are enabled by pixel-level processing, the applications of which promise to further improve CMOS image sensor performance and broaden their applicability beyond current markets.
748 citations
Cites background from "Active Pixel Sensors: Are CCD's Din..."
...In the early 1990s, work began on the modern CMOS active pixel sensor (APS), conceived originally in 1968 [4], [5]....
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Patent•
12 Mar 2003TL;DR: In this paper, an imaging device is formed as a monolithic complementary metal oxide semiconductor integrated circuit in an industry standard complementary MOS semiconductor process, the integrated circuit including a focal plane array of pixel cells, each one of the cells including a photogate overlying the substrate for accumulating photo-generated charge in an underlying portion of the substrate, a readout circuit including at least an output field effect transistor formed in the substrate and a charge coupled device section formed on the substrate adjacent the photrogate having a sensing node connected to the output transistor and at least one charge coupled
Abstract: An imaging device formed as a monolithic complementary metal oxide semiconductor integrated circuit in an industry standard complementary metal oxide semiconductor process, the integrated circuit including a focal plane array of pixel cells, each one of the cells including a photogate overlying the substrate for accumulating photo-generated charge in an underlying portion of the substrate, a readout circuit including at least an output field effect transistor formed in the substrate, and a charge coupled device section formed on the substrate adjacent the photogate having a sensing node connected to the output transistor and at least one charge coupled device stage for transferring charge from the underlying portion of the substrate to the sensing node.
714 citations
References
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TL;DR: The characterization of surface channel charge-coupled device line imagers with front-surface imaging, interline transfer, and 2-phase stepped oxide, silicon-gate CCD registers is presented in this paper.
Abstract: The characterization of surface channel charge-coupled device line imagers with front-surface imaging, interline transfer, and 2-phase stepped oxide, silicon-gate CCD registers is presented. The analysis, design, and evaluation of 1/spl times/64 CCD line arrays are described in terms of their performance at low light levels. The authors describe the responsivity, resolution, spectral, and noise measurements on silicon-gate CCD sensors and CCD interline shift-registers. The influence of transfer inefficiency and electrical fat-zero insertion on resolution and noise is described at low light levels.
342 citations
Book•
01 Jan 1975
TL;DR: It is projected that charge transfer devices will rapidly find their way into certain analog delay, image sensing, and digital applications.
Abstract: This is a review describing the use of charge transfer devices for digital memory, analog delay, and image sensing. Short descriptions of different types of charge-coupled devices and MOS bucket-brigade devices are presented. Those factors such as transfer inefficiency, noise, and dark current which affect the performance of these devices in the above applications are discussed. Various possible organizations of charge transfer devices to serve different functions are described. Many charge transfer devices have been fabricated and already indicate a high degree of achievement. Transfer inefficiencies per transfer in the range 10−3 to 10−4 have been measured. Finally, it is projected that charge transfer devices will rapidly find their way into certain analog delay, image sensing, and digital applications.
257 citations
01 Jan 1991
TL;DR: In this article, the requirements for infrared focal plane arrays (IRFPAs) for advanced infrared imaging systems are discussed, and an overview is given of different IRFPA architectures, including photoconductive, photovoltaic, metal insulator-semiconductor (MIS), and Schottky barrier.
Abstract: Requirements for infrared focal plane arrays (IRFPAs) for advanced infrared imaging systems are discussed, and an overview is given of different IRFPA architectures. Important IR detector structures, including photoconductive, photovoltaic, metal-insulator-semiconductor (MIS), and Schottky barrier, are reviewed. Infrared detector materials and related crystal-growth techniques are discussed, emphasizing applicability to IRFPA designs and performance. Three types of input circuit used to couple the detector to the readout circuitry are discussed, namely, direct injection, buffered direct injection, and gate modulation. An overview is given of several readout techniques, including the CCD, MOSFET switch, CID, and CIM. Also discussed are related onchip signal processing topics as well as questions regarding producibility and array implementation. >
248 citations
TL;DR: In this article, a technique for operating a p-n junction photodiode in a photon flux integration mode is described, where the voltage across the junction will decay at a rate that is independent of junction area.
Abstract: A technique for operating a p-n junction photodiode in a photon flux integration mode is described. In this mode the p-n junction is charged to a reverse voltage (less than its breakdown voltage) and then open-circuited. The voltage across the junction, with zero incident illumination, will decay at a rate that is independent of junction area. Time constants in the order of seconds may be achieved with silicon planar structures at room temperature. Under illumination, the rate of decay of charge depends linearly on the intensity of the incident illumination, so that the total charge removed is proportional to the time integral of illumination. Operation of p-n junction photodiodes is analyzed for this mode and boundary conditions are established. A practical structure utilizing this mode of operation is discussed. This structure makes use of the nearly ideal switch characteristics of an insulated gate field-effect transistor to periodically sample a photodiode. Advantages offered by this device structure include 1) linear dependence of signal charge on light intensity over several orders of magnitude; 2) electronically controllable sensitivity; 3) ease of integration into arrays for image sensing.
227 citations