The Experts below are selected from a list of 231 Experts worldwide ranked by ideXlab platform

Bernabe Linares-barranco - One of the best experts on this subject based on the ideXlab platform.

  • ISCAS - A signed Spatial Contrast event spike retina chip
    Proceedings of 2010 IEEE International Symposium on Circuits and Systems, 2010
    Co-Authors: Juan A. Lenero-bardallo, Teresa Serrano-gotarredona, Bernabe Linares-barranco
    Abstract:

    Reported AER (Address Event Representation) Contrast retinae perform a Contrast computation based on the ratio between a pixel's local light intensity and a Spatially weighted average of its neighbourhood. This results in compact circuits, but with the penalty of all pixels generating output signals even if they sense no Contrast. In this paper we present a Spatial Contrast retina with bipolar output: Contrast is computed as the relative normalized difference (not the ratio) between a pixel's local light and its weighted Spatial average, normalized to average light. As a result, Contrast includes a sign, is ambient light independent, and the output will be zero if there is no Contrast. Furthermore, an adjustable thresholding mechanism has been included, such that pixels remain silent until they sense an absolute Contrast above the adjustable threshold. The pixel Contrast computation circuit is based on Boahen's Biharmonic operator Contrast circuit, which has been improved to include mismatch calibration and adaptive current based biasing. As a result, the Contrast computation circuit shows much less mismatch, is almost insensitive to ambient light illumination, and biasing is much less critical than in the original voltage biasing scheme. The retina also includes an optional TFS (Time-to-First-Spike) integration mode. A full AER retina version has been fabricated and tested. In the present paper we provide preliminary experimental results.

  • ESSCIRC - A 100dB dynamic range event-driven Spatial Contrast sensor with 100μs response time and Time-to-First-Spike mode
    2010 Proceedings of ESSCIRC, 2010
    Co-Authors: Juan A. Lenero-bardallo, Teresa Serrano-gotarredona, Bernabe Linares-barranco
    Abstract:

    Bio-inspired vision sensors have some inherent advantages over conventional sequential-still-image sensors. Some of them are high speed, low latency and reduced bandwidth and power consumption. In this paper, we present a new Spatial Contrast retina with signed output. Its output is zero if there is no Contrast. The new sensor includes an optional Time-to-First-Spike mode (TFS) that combines the advantages of AER vision systems and frame-based ones. In TFS mode, times between consecutive frames can be adjusted dynamically by transmitting only relevant information. Both operation modes are ambient-light-independent, to first order. A 32×32 pixel prototype has been fabricated in 0.35um CMOS. Experimental results are provided.

  • A Five-Decade Dynamic-Range Ambient-Light-Independent Calibrated Signed-Spatial-Contrast AER Retina With 0.1-ms Latency and Optional Time-to-First-Spike Mode
    IEEE Transactions on Circuits and Systems I: Regular Papers, 2010
    Co-Authors: Juan A. Lenero-bardallo, Teresa Serrano-gotarredona, Bernabe Linares-barranco
    Abstract:

    Address Event Representation (AER) is an emergent technology for assembling modular multiblock bio-inspired sensory and processing systems. Visual sensors (retinae) are among the first AER modules to be reported since the introduction of the technology. Spatial-Contrast AER retinae are of special interest since they provide highly compressed data flow without reducing the relevant information required for performing recognition. The reported AER Contrast retinae perform a Contrast computation based on the ratio between a pixel's local light intensity and a Spatially weighted average of its neighborhood. This resulted in compact circuits but with the penalty of all pixels generating output signals even if they sensed no Contrast. In this paper, we present a Spatial-Contrast retina with a signed output: Contrast is computed as the relative difference (not the ratio) between a pixel's local light and its surrounding Spatial average and normalized with respect to ambient light. As a result, Contrast is ambient light independent, includes a sign, and the output will be zero if there is no Contrast. Furthermore, an adjustable thresholding mechanism has been included, such that pixels remain silent until they sense an absolute Contrast above the adjustable threshold. The pixel Contrast-computation circuit is based on Boahen's biharmonic operator Contrast circuit, which has been improved to include mismatch calibration and adaptive-current-based biasing. As a result, the Contrast-computation circuit shows much less mismatch, is almost insensitive to ambient light illumination, and biasing is much less critical than in the original voltage biasing scheme. The retina includes an optional global reset mechanism for operation in ambient-light-independent Time-to-First-Spike Contrast-computation mode. A 32 32 pixel test prototype has been fabricated in 0.35-m CMOS. Experimental results are provided.

  • ISCAS - A mismatch calibrated bipolar Spatial Contrast AER retina with adjustable Contrast threshold
    2009 IEEE International Symposium on Circuits and Systems, 2009
    Co-Authors: Juan A. Lenero-bardallo, Teresa Serrano-gotarredona, Bernabe Linares-barranco
    Abstract:

    Address Event Representation (AER) is an emergent technology for assembling modular multi-blocks bio-inspired sensory and processing systems. Visual sensors (retinae) are among the first AER modules to be reported since the introduction of the technology. Spatial Contrast AER retinae are of special interest since they provide highly compressed data flow without reducing the relevant information required for performing recognition. Reported AER Contrast retinae perform a Contrast computation based on the ratio between a pixel's local light intensity and a Spatially weighted average of its neighbourhood. This resulted in compact circuits, but with the penalty of all pixels generating output signals even if they sensed no Contrast. In this paper we present a Spatial Contrast retina with bipolar output: Contrast is computed as the relative difference between a pixel's local light and its weighted Spatial average. As a result, Contrast includes a sign and the output will be zero if there is no Contrast. Furthermore, an adjustable thresholding mechanism has been included, such that pixels remain silent until they sense an absolute Contrast above the adjustable threshold. The pixel Contrast computation circuit is based on Boahen's Biharmonic operator Contrast circuit, which has been improved to include mismatch calibration and adaptive current based biasing. As a result, the Contrast computation circuit shows much less mismatch, is almost insensitive to ambient light illumination, and biasing is much less critical than in the original voltage biasing scheme. A full AER retina version has been submitted for fabrication. In the present paper we provide simulation results.

  • A Spatial Contrast Retina With On-Chip Calibration for Neuromorphic Spike-Based AER Vision Systems
    IEEE Transactions on Circuits and Systems I: Regular Papers, 2007
    Co-Authors: J. Costas-santos, Teresa Serrano-gotarredona, R. Serrano-gotarredona, Bernabe Linares-barranco
    Abstract:

    We present a 32 times 32 pixels Contrast retina microchip that provides its output as an address event representation (AER) stream. Spatial Contrast is computed as the ratio between pixel photocurrent and a local average between neighboring pixels obtained with a diffuser network. This current-based computation produces an important amount of mismatch between neighboring pixels, because the currents can be as low as a few pico-amperes. Consequently, a compact calibration circuitry has been included to trimm each pixel. Measurements show a reduction in mismatch standard deviation from 57% to 6.6% (indoor light). The paper describes the design of the pixel with its Spatial Contrast computation and calibration sections. About one third of pixel area is used for a 5-bit calibration circuit. Area of pixel is 58 mum times 56 mum , while its current consumption is about 20 nA at 1-kHz event rate. Extensive experimental results are provided for a prototype fabricated in a standard 0.35-mum CMOS process.

Maria Grazia Tardini - One of the best experts on this subject based on the ideXlab platform.

  • improvement of Spatial Contrast sensitivity threshold after surgical reduction of intraocular pressure in unilateral high tension glaucoma
    Investigative Ophthalmology & Visual Science, 2005
    Co-Authors: Stefano A Gandolfi, Luca Cimino, C Sangermani, Nicola Ungaro, Paolo Mora, Maria Grazia Tardini
    Abstract:

    PUKPOSE. To measure the effect of a surgical reduction of IOP on the Spatial Contrast sensitivity threshold in eyes showing a considerably increased IOP but no glaucomatous visual field defect, on white-on-white computer-assisted static perimetry. METHODS. Prospective clinical trial, lasting 36 months; 10 consecutive subjects with untreated IOP ≥ 30 mm Hg in one eye and <18 mm Hg in the fellow eye, no evidence of field damage in both eyes, best corrected visual acuity ≥ 20/20 in both eyes, and scheduled for a primary trabeculectomy in the eye showing a high IOP. The Spatial Contrast sensitivity threshold was measured before surgery and at each follow-up visit. RESULTS. Preoperative Spatial Contrast sensitivity was worse in those eyes bearing a high IOP relative to the normal fellow eyes (paired samples t-test, P < 0.0005). An improvement of Contrast sensitivity threshold, exceeding the 95% confidence limits of the preoperative test-retest variability, was observed at 3, 6, and 12 cyc/deg in each surgical eye at the end of follow-up. No change was observed in the fellow untreated normal eyes. The improvement correlated directly with the amount of decrease in pressure obtained by surgery. CONCLUSIONS. Eyes with no field defects on white-on-white computer-assisted static perimetry, but bearing a IOP ≥ 30 mm Hg, show a decreased Spatial Contrast sensitivity. A surgically obtained reduction of IOP is paralleled by an improvement of Spatial Contrast sensitivity.

  • Improvement of Spatial Contrast sensitivity threshold after surgical reduction of intraocular pressure in unilateral high-tension glaucoma.
    Investigative Opthalmology & Visual Science, 2005
    Co-Authors: Stefano A Gandolfi, Luca Cimino, C Sangermani, Nicola Ungaro, Paolo Mora, Maria Grazia Tardini
    Abstract:

    PUKPOSE. To measure the effect of a surgical reduction of IOP on the Spatial Contrast sensitivity threshold in eyes showing a considerably increased IOP but no glaucomatous visual field defect, on white-on-white computer-assisted static perimetry. METHODS. Prospective clinical trial, lasting 36 months; 10 consecutive subjects with untreated IOP ≥ 30 mm Hg in one eye and

Stefano A Gandolfi - One of the best experts on this subject based on the ideXlab platform.

  • improvement of Spatial Contrast sensitivity threshold after surgical reduction of intraocular pressure in unilateral high tension glaucoma
    Investigative Ophthalmology & Visual Science, 2005
    Co-Authors: Stefano A Gandolfi, Luca Cimino, C Sangermani, Nicola Ungaro, Paolo Mora, Maria Grazia Tardini
    Abstract:

    PUKPOSE. To measure the effect of a surgical reduction of IOP on the Spatial Contrast sensitivity threshold in eyes showing a considerably increased IOP but no glaucomatous visual field defect, on white-on-white computer-assisted static perimetry. METHODS. Prospective clinical trial, lasting 36 months; 10 consecutive subjects with untreated IOP ≥ 30 mm Hg in one eye and <18 mm Hg in the fellow eye, no evidence of field damage in both eyes, best corrected visual acuity ≥ 20/20 in both eyes, and scheduled for a primary trabeculectomy in the eye showing a high IOP. The Spatial Contrast sensitivity threshold was measured before surgery and at each follow-up visit. RESULTS. Preoperative Spatial Contrast sensitivity was worse in those eyes bearing a high IOP relative to the normal fellow eyes (paired samples t-test, P < 0.0005). An improvement of Contrast sensitivity threshold, exceeding the 95% confidence limits of the preoperative test-retest variability, was observed at 3, 6, and 12 cyc/deg in each surgical eye at the end of follow-up. No change was observed in the fellow untreated normal eyes. The improvement correlated directly with the amount of decrease in pressure obtained by surgery. CONCLUSIONS. Eyes with no field defects on white-on-white computer-assisted static perimetry, but bearing a IOP ≥ 30 mm Hg, show a decreased Spatial Contrast sensitivity. A surgically obtained reduction of IOP is paralleled by an improvement of Spatial Contrast sensitivity.

  • Improvement of Spatial Contrast sensitivity threshold after surgical reduction of intraocular pressure in unilateral high-tension glaucoma.
    Investigative Opthalmology & Visual Science, 2005
    Co-Authors: Stefano A Gandolfi, Luca Cimino, C Sangermani, Nicola Ungaro, Paolo Mora, Maria Grazia Tardini
    Abstract:

    PUKPOSE. To measure the effect of a surgical reduction of IOP on the Spatial Contrast sensitivity threshold in eyes showing a considerably increased IOP but no glaucomatous visual field defect, on white-on-white computer-assisted static perimetry. METHODS. Prospective clinical trial, lasting 36 months; 10 consecutive subjects with untreated IOP ≥ 30 mm Hg in one eye and

Juan A. Lenero-bardallo - One of the best experts on this subject based on the ideXlab platform.

  • ESSCIRC - A 100dB dynamic range event-driven Spatial Contrast sensor with 100μs response time and Time-to-First-Spike mode
    2010 Proceedings of ESSCIRC, 2010
    Co-Authors: Juan A. Lenero-bardallo, Teresa Serrano-gotarredona, Bernabe Linares-barranco
    Abstract:

    Bio-inspired vision sensors have some inherent advantages over conventional sequential-still-image sensors. Some of them are high speed, low latency and reduced bandwidth and power consumption. In this paper, we present a new Spatial Contrast retina with signed output. Its output is zero if there is no Contrast. The new sensor includes an optional Time-to-First-Spike mode (TFS) that combines the advantages of AER vision systems and frame-based ones. In TFS mode, times between consecutive frames can be adjusted dynamically by transmitting only relevant information. Both operation modes are ambient-light-independent, to first order. A 32×32 pixel prototype has been fabricated in 0.35um CMOS. Experimental results are provided.

  • ISCAS - A signed Spatial Contrast event spike retina chip
    Proceedings of 2010 IEEE International Symposium on Circuits and Systems, 2010
    Co-Authors: Juan A. Lenero-bardallo, Teresa Serrano-gotarredona, Bernabe Linares-barranco
    Abstract:

    Reported AER (Address Event Representation) Contrast retinae perform a Contrast computation based on the ratio between a pixel's local light intensity and a Spatially weighted average of its neighbourhood. This results in compact circuits, but with the penalty of all pixels generating output signals even if they sense no Contrast. In this paper we present a Spatial Contrast retina with bipolar output: Contrast is computed as the relative normalized difference (not the ratio) between a pixel's local light and its weighted Spatial average, normalized to average light. As a result, Contrast includes a sign, is ambient light independent, and the output will be zero if there is no Contrast. Furthermore, an adjustable thresholding mechanism has been included, such that pixels remain silent until they sense an absolute Contrast above the adjustable threshold. The pixel Contrast computation circuit is based on Boahen's Biharmonic operator Contrast circuit, which has been improved to include mismatch calibration and adaptive current based biasing. As a result, the Contrast computation circuit shows much less mismatch, is almost insensitive to ambient light illumination, and biasing is much less critical than in the original voltage biasing scheme. The retina also includes an optional TFS (Time-to-First-Spike) integration mode. A full AER retina version has been fabricated and tested. In the present paper we provide preliminary experimental results.

  • A Five-Decade Dynamic-Range Ambient-Light-Independent Calibrated Signed-Spatial-Contrast AER Retina With 0.1-ms Latency and Optional Time-to-First-Spike Mode
    IEEE Transactions on Circuits and Systems I: Regular Papers, 2010
    Co-Authors: Juan A. Lenero-bardallo, Teresa Serrano-gotarredona, Bernabe Linares-barranco
    Abstract:

    Address Event Representation (AER) is an emergent technology for assembling modular multiblock bio-inspired sensory and processing systems. Visual sensors (retinae) are among the first AER modules to be reported since the introduction of the technology. Spatial-Contrast AER retinae are of special interest since they provide highly compressed data flow without reducing the relevant information required for performing recognition. The reported AER Contrast retinae perform a Contrast computation based on the ratio between a pixel's local light intensity and a Spatially weighted average of its neighborhood. This resulted in compact circuits but with the penalty of all pixels generating output signals even if they sensed no Contrast. In this paper, we present a Spatial-Contrast retina with a signed output: Contrast is computed as the relative difference (not the ratio) between a pixel's local light and its surrounding Spatial average and normalized with respect to ambient light. As a result, Contrast is ambient light independent, includes a sign, and the output will be zero if there is no Contrast. Furthermore, an adjustable thresholding mechanism has been included, such that pixels remain silent until they sense an absolute Contrast above the adjustable threshold. The pixel Contrast-computation circuit is based on Boahen's biharmonic operator Contrast circuit, which has been improved to include mismatch calibration and adaptive-current-based biasing. As a result, the Contrast-computation circuit shows much less mismatch, is almost insensitive to ambient light illumination, and biasing is much less critical than in the original voltage biasing scheme. The retina includes an optional global reset mechanism for operation in ambient-light-independent Time-to-First-Spike Contrast-computation mode. A 32 32 pixel test prototype has been fabricated in 0.35-m CMOS. Experimental results are provided.

  • ISCAS - A mismatch calibrated bipolar Spatial Contrast AER retina with adjustable Contrast threshold
    2009 IEEE International Symposium on Circuits and Systems, 2009
    Co-Authors: Juan A. Lenero-bardallo, Teresa Serrano-gotarredona, Bernabe Linares-barranco
    Abstract:

    Address Event Representation (AER) is an emergent technology for assembling modular multi-blocks bio-inspired sensory and processing systems. Visual sensors (retinae) are among the first AER modules to be reported since the introduction of the technology. Spatial Contrast AER retinae are of special interest since they provide highly compressed data flow without reducing the relevant information required for performing recognition. Reported AER Contrast retinae perform a Contrast computation based on the ratio between a pixel's local light intensity and a Spatially weighted average of its neighbourhood. This resulted in compact circuits, but with the penalty of all pixels generating output signals even if they sensed no Contrast. In this paper we present a Spatial Contrast retina with bipolar output: Contrast is computed as the relative difference between a pixel's local light and its weighted Spatial average. As a result, Contrast includes a sign and the output will be zero if there is no Contrast. Furthermore, an adjustable thresholding mechanism has been included, such that pixels remain silent until they sense an absolute Contrast above the adjustable threshold. The pixel Contrast computation circuit is based on Boahen's Biharmonic operator Contrast circuit, which has been improved to include mismatch calibration and adaptive current based biasing. As a result, the Contrast computation circuit shows much less mismatch, is almost insensitive to ambient light illumination, and biasing is much less critical than in the original voltage biasing scheme. A full AER retina version has been submitted for fabrication. In the present paper we provide simulation results.

Teresa Serrano-gotarredona - One of the best experts on this subject based on the ideXlab platform.

  • ISCAS - A signed Spatial Contrast event spike retina chip
    Proceedings of 2010 IEEE International Symposium on Circuits and Systems, 2010
    Co-Authors: Juan A. Lenero-bardallo, Teresa Serrano-gotarredona, Bernabe Linares-barranco
    Abstract:

    Reported AER (Address Event Representation) Contrast retinae perform a Contrast computation based on the ratio between a pixel's local light intensity and a Spatially weighted average of its neighbourhood. This results in compact circuits, but with the penalty of all pixels generating output signals even if they sense no Contrast. In this paper we present a Spatial Contrast retina with bipolar output: Contrast is computed as the relative normalized difference (not the ratio) between a pixel's local light and its weighted Spatial average, normalized to average light. As a result, Contrast includes a sign, is ambient light independent, and the output will be zero if there is no Contrast. Furthermore, an adjustable thresholding mechanism has been included, such that pixels remain silent until they sense an absolute Contrast above the adjustable threshold. The pixel Contrast computation circuit is based on Boahen's Biharmonic operator Contrast circuit, which has been improved to include mismatch calibration and adaptive current based biasing. As a result, the Contrast computation circuit shows much less mismatch, is almost insensitive to ambient light illumination, and biasing is much less critical than in the original voltage biasing scheme. The retina also includes an optional TFS (Time-to-First-Spike) integration mode. A full AER retina version has been fabricated and tested. In the present paper we provide preliminary experimental results.

  • ESSCIRC - A 100dB dynamic range event-driven Spatial Contrast sensor with 100μs response time and Time-to-First-Spike mode
    2010 Proceedings of ESSCIRC, 2010
    Co-Authors: Juan A. Lenero-bardallo, Teresa Serrano-gotarredona, Bernabe Linares-barranco
    Abstract:

    Bio-inspired vision sensors have some inherent advantages over conventional sequential-still-image sensors. Some of them are high speed, low latency and reduced bandwidth and power consumption. In this paper, we present a new Spatial Contrast retina with signed output. Its output is zero if there is no Contrast. The new sensor includes an optional Time-to-First-Spike mode (TFS) that combines the advantages of AER vision systems and frame-based ones. In TFS mode, times between consecutive frames can be adjusted dynamically by transmitting only relevant information. Both operation modes are ambient-light-independent, to first order. A 32×32 pixel prototype has been fabricated in 0.35um CMOS. Experimental results are provided.

  • A Five-Decade Dynamic-Range Ambient-Light-Independent Calibrated Signed-Spatial-Contrast AER Retina With 0.1-ms Latency and Optional Time-to-First-Spike Mode
    IEEE Transactions on Circuits and Systems I: Regular Papers, 2010
    Co-Authors: Juan A. Lenero-bardallo, Teresa Serrano-gotarredona, Bernabe Linares-barranco
    Abstract:

    Address Event Representation (AER) is an emergent technology for assembling modular multiblock bio-inspired sensory and processing systems. Visual sensors (retinae) are among the first AER modules to be reported since the introduction of the technology. Spatial-Contrast AER retinae are of special interest since they provide highly compressed data flow without reducing the relevant information required for performing recognition. The reported AER Contrast retinae perform a Contrast computation based on the ratio between a pixel's local light intensity and a Spatially weighted average of its neighborhood. This resulted in compact circuits but with the penalty of all pixels generating output signals even if they sensed no Contrast. In this paper, we present a Spatial-Contrast retina with a signed output: Contrast is computed as the relative difference (not the ratio) between a pixel's local light and its surrounding Spatial average and normalized with respect to ambient light. As a result, Contrast is ambient light independent, includes a sign, and the output will be zero if there is no Contrast. Furthermore, an adjustable thresholding mechanism has been included, such that pixels remain silent until they sense an absolute Contrast above the adjustable threshold. The pixel Contrast-computation circuit is based on Boahen's biharmonic operator Contrast circuit, which has been improved to include mismatch calibration and adaptive-current-based biasing. As a result, the Contrast-computation circuit shows much less mismatch, is almost insensitive to ambient light illumination, and biasing is much less critical than in the original voltage biasing scheme. The retina includes an optional global reset mechanism for operation in ambient-light-independent Time-to-First-Spike Contrast-computation mode. A 32 32 pixel test prototype has been fabricated in 0.35-m CMOS. Experimental results are provided.

  • ISCAS - A mismatch calibrated bipolar Spatial Contrast AER retina with adjustable Contrast threshold
    2009 IEEE International Symposium on Circuits and Systems, 2009
    Co-Authors: Juan A. Lenero-bardallo, Teresa Serrano-gotarredona, Bernabe Linares-barranco
    Abstract:

    Address Event Representation (AER) is an emergent technology for assembling modular multi-blocks bio-inspired sensory and processing systems. Visual sensors (retinae) are among the first AER modules to be reported since the introduction of the technology. Spatial Contrast AER retinae are of special interest since they provide highly compressed data flow without reducing the relevant information required for performing recognition. Reported AER Contrast retinae perform a Contrast computation based on the ratio between a pixel's local light intensity and a Spatially weighted average of its neighbourhood. This resulted in compact circuits, but with the penalty of all pixels generating output signals even if they sensed no Contrast. In this paper we present a Spatial Contrast retina with bipolar output: Contrast is computed as the relative difference between a pixel's local light and its weighted Spatial average. As a result, Contrast includes a sign and the output will be zero if there is no Contrast. Furthermore, an adjustable thresholding mechanism has been included, such that pixels remain silent until they sense an absolute Contrast above the adjustable threshold. The pixel Contrast computation circuit is based on Boahen's Biharmonic operator Contrast circuit, which has been improved to include mismatch calibration and adaptive current based biasing. As a result, the Contrast computation circuit shows much less mismatch, is almost insensitive to ambient light illumination, and biasing is much less critical than in the original voltage biasing scheme. A full AER retina version has been submitted for fabrication. In the present paper we provide simulation results.

  • A Spatial Contrast Retina With On-Chip Calibration for Neuromorphic Spike-Based AER Vision Systems
    IEEE Transactions on Circuits and Systems I: Regular Papers, 2007
    Co-Authors: J. Costas-santos, Teresa Serrano-gotarredona, R. Serrano-gotarredona, Bernabe Linares-barranco
    Abstract:

    We present a 32 times 32 pixels Contrast retina microchip that provides its output as an address event representation (AER) stream. Spatial Contrast is computed as the ratio between pixel photocurrent and a local average between neighboring pixels obtained with a diffuser network. This current-based computation produces an important amount of mismatch between neighboring pixels, because the currents can be as low as a few pico-amperes. Consequently, a compact calibration circuitry has been included to trimm each pixel. Measurements show a reduction in mismatch standard deviation from 57% to 6.6% (indoor light). The paper describes the design of the pixel with its Spatial Contrast computation and calibration sections. About one third of pixel area is used for a 5-bit calibration circuit. Area of pixel is 58 mum times 56 mum , while its current consumption is about 20 nA at 1-kHz event rate. Extensive experimental results are provided for a prototype fabricated in a standard 0.35-mum CMOS process.