Wide-Dynamic-Range CMOS Image Sensors—Comparative Performance Analysis (original) (raw)
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Wide-Dynamic-Range CMOS Image Sensors—Comparative Performance Analysis
IEEE Transactions on Electron Devices, 2000
A large variety of solutions for widening the dynamic range (DR) of CMOS image sensors has been proposed throughout the years. We propose a set of criteria upon which an effective comparative analysis of the performance of wide-DR (WDR) sensors can be done. Sensors for WDR are divided into seven categories: 1) companding sensors; 2) multimode sensors; 3) clipping sensors; 4) frequency-based sensors; 5) time-to-saturation (timeto-first spike) sensors; 6) global-control-over-the-integration-time sensors; and 7) autonomous-control-over-the-integration-time sensors. The comparative analysis for each category is based upon the quantitative assessments of the following parameters: signalto-noise ratio, DR extension, noise floor, minimal transistor count, and sensitivity. These parameters are assessed using consistent assumptions and definitions, which are common to all WDR sensor categories. The advantages and disadvantages of each category in the sense of power consumption and data rate are discussed qualitatively. The influence of technology advancements on the proposed set of criteria is discussed as well.
Optical Engineering, 1999
The work done to provide images sensors (CCDs and CMOS) with a wide dynamic range is reviewed. The different classes of solutions, which consist of logarithmic sensors, `clipped' sensors, multimode sensors, frequency-based sensors, and sensors with control over integration time are described. The pros and cons of each solution are discussed, and some new experimental results are shown. Active pixel
A Tunable CMOS Image Sensor with High Fill-Factor for High Dynamic Range Applications
7th International Electronic Conference on Sensors and Applications, 2020
Several CMOS imager sensors were proposed to obtain high dynamic range imager (>100 dB). However, as drawback these imagers implement a large number of transistors per pixel resulting in a low fill factor, high power consumption and high complexity CMOS image sensors. In this work, a new operation mode for 3 T CMOS image sensors is presented for high dynamic range (HDR) applications. The operation mode consists of biasing the conventional reset transistor as active load to photodiode generating a reference current. The output voltage achieves a steady state when the photocurrent becomes equal to the reference current, similar to the inverter operation in the transition region. At a specific bias voltage, the output swings from o to Vdd in a small light intensity range; however, high dynamic range is achieve using multiple readout at different bias voltage. For high dynamic range operation different values of bias voltage can be applied from each one, and the signal can be captured to compose a high dynamic range image. Compared to other high dynamic range architectures this proposed CMOS image pixel show as advantage high fillfactor (3 T) and lower complexity. Moreover, as the CMOS pixel does not operate in integration mode, de readout can be performed at higher speed. A prototype was fabricated at 3.3 V 0.35 µm CMOS technology. Experimental results are shown by applying five different control voltage from 0.65 to 1.2 V is possible to obtain a dynamic range of about 100 dB.
A wide dynamic range CMOS digital pixel sensor
A CMOS image sensor with pixel level analog to digital conversion is presented. Each 13.8µm x 13.8µm pixel area contains a photodiode and a dynamic comparator using the maximum voltage swing available (0V -1.8V). The comparator does not need any bias current and is insensitive to fabrication process variations. Also a digital to analog converter (DAC) is used to deliver a voltage reference in order to compare it with the pixel voltage for the analog to digital conversion. This DAC provides the possibility to convert the pixel voltage linearly or to compress it logarithmically. The circuit allows image captures at multiple exposure times, and the resulting values are delivered in floating digital format, offering the possibility to expand the intrascene dynamic range to more than 84 dB. The circuit was implemented in a CMOS 0.18µm process and has been submitted for fabrication.
A wide dynamic range CMOS image sensor with pulse-frequency-modulation and in-pixel amplification
Microelectronics Journal, 2009
This paper briefly examines the pros and cons of CMOS pulse-frequency-modulation (PFM) digital pixel sensors. A pulse-frequency-modulation digital pixel sensor with in-pixel amplification is proposed to improve the resolution of the pixel sensor at low illumination. The proposed PFM digital pixel sensor offers the characteristics of a reduced integration time when the level of illumination is low with the fill factor comparable to that of PFM digital pixel sensors without in-pixel amplification. The proposed digital image sensor has been designed in TSMC-0:18 mm 1.8 V CMOS technology and validated using Spectre from Cadence Design Systems with BSIM3V3 device models. Simulation results demonstrate that the dynamic range of the proposed PFM digital pixel sensor with in-pixel amplification is 20 dB larger as compared with that of PFM digital pixel sensors without in-pixel amplification. The increased dynamic range is obtained in the low illumination condition where PFM digital pixel sensors without in-pixel amplification cease the operation due to the low photo current.
Microelectronics Journal, 2006
The role of CMOS Image Sensors since their birth around the 1960s, has been changing a lot. Unlike the past, current CMOS Image Sensors are becoming competitive with regard to Charged Couple Device (CCD) technology. They offer many advantages with respect to CCD, such as lower power consumption, lower voltage operation, on-chip functionality and lower cost. Nevertheless, they are still too noisy and less sensitive than CCDs.
High-sensitivity high-dynamic digital CMOS imager
Proceedings of …, 2001
CMOS image sensors offer over the standard and ubiquitous charge-coupled devices several advantages, in terms of power consumption, miniaturization, on-chip integration of analog-to-digital converters and signal processing for dedicated functionality. Due to the typically ...
Toshiba Dynastron-WD™ Wide Dynamic Range Technology for CMOS Image Sensors Highlights
• To date, image sensor vendors have focused on delivering low-light performance, but there is increased demand for high-quality performance under bright light conditions as well. • When the pixel wells are full, they overflow and detail is lost, a phenomenon called blooming. A wide dynamic range sensor can avoid such problems and capture a much higher level of detail than a normal sensor can. • The Toshiba Dynastron-WD technology can extend dynamic range of a CMOS image sensor up to 96dB. It is a critical capability in today's highly competitive camera phone market.
Analog Encoding Voltage—A Key to Ultra-Wide Dynamic Range and Low Power CMOS Image Sensor
Journal of Low Power Electronics and Applications, 2013
Usually Wide Dynamic Range (WDR) sensors that autonomously adjust their integration time to fit intra-scene illumination levels use a separate digital memory unit. This memory contains the data needed for the dynamic range. Motivated by the demands for low power and chip area reduction, we propose a different implementation of the aforementioned WDR algorithm by replacing the external digital memory with an analog in-pixel memory. This memory holds the effective integration time represented by analog encoding voltage (AEV). In addition, we present a "ranging" scheme of configuring the pixel integration time in which the effective integration time is configured at the first half of the frame. This enables a substantial simplification of the pixel control during the rest of the frame and thus allows for a significantly more remarkable DR extension. Furthermore, we present the implementation of "ranging" and AEV concepts on two different designs, which are targeted to reach five and eight decades of DR, respectively. We describe in detail the operation of both systems and provide the post-layout simulation results for the second solution. The simulations show that the second design reaches DR up to 170 dBs. We also provide a comparative analysis in terms of the number of operations per pixel required by our solution and by other widespread WDR algorithms. Based on the OPEN ACCESS J. Low Power Electron. Appl. 2013, 3 28 calculated results, we conclude that the proposed two designs, using "ranging" and AEV concepts, are attractive, since they obtain a wide dynamic range at high operation speed and low power consumption.
Advanced cmos based image sensors
Complementary Metal Oxide Semiconductor (CMOS) Image Sensors technology since their innovation has been changed a lot. Previously, CMOS technology was not so powerful to be considered as the competitor with couple charged devices. However, current CMOS Image Sensors (CIS) gain a huge market share by offering many advantages such as lower voltage operation, on-chip functionality and low cost. Nevertheless, they have the noise and low sensitivity problems. There are variousCIS to satisfy the huge demand in different areas, such as digital photography, industrial vision, medical and space applications, electrostatic sensing, automotive, instrumentation and 3D vision systems. Recently, a lot of research is done to solve the problems of sensitivity, noise, power consumption, voltage operation, speed imaging and dynamic range. In this paper, advanced CIS are reviewed, gathering data on the newest advances, their applications and the recent challenges.