title: Illumination waveform optimization for time-of-flight range imaging cameras

authors: Payne, Andrew D.

subjects: time of flight

abstract: Time-of-flight range imaging sensors acquire an image of a scene, where in addition to standard intensity information, the range (or distance) is also measured concurrently by each pixel. Range is measured using a correlation technique, where an amplitude modulated light source illuminates the scene and the reflected light is sampled by a gain modulated image sensor. Typically the illumination source and image sensor are amplitude modulated with square waves, leading to a range measurement linearity error caused by aliased harmonic components within the correlation waveform. A simple method to improve measurement linearity by reducing the duty cycle of the illumination waveform to suppress problematic aliased harmonic components is demonstrated. If the total optical power is kept constant, the measured correlation waveform amplitude also increases at these reduced illumination duty cycles. Measurement performance is evaluated over a range of illumination duty cycles, both for a standard range imaging camera configuration, and also using a more complicated phase encoding method that is designed to cancel aliased harmonics during the sampling process. The standard configuration benefits from improved measurement linearity for illumination duty cycles around 30%, while the measured amplitude, hence range precision, is increased for both methods as the duty cycle is reduced below 50% (while maintaining constant optical power).

text: Illumination waveform optimization for time-of-flight range imaging cameras Time-of-flight range imaging sensors acquire an image of a scene, where in addition to standard intensity information, the range (or distance) is also measured concurrently by each pixel. Range is measured using a correlation technique, where an amplitude modulated light source illuminates the scene and the reflected light is sampled by a gain modulated image sensor. Typically the illumination source and image sensor are amplitude modulated with square waves, leading to a range measurement linearity error caused by aliased harmonic components within the correlation waveform. A simple method to improve measurement linearity by reducing the duty cycle of the illumination waveform to suppress problematic aliased harmonic components is demonstrated. If the total optical power is kept constant, the measured correlation waveform amplitude also increases at these reduced illumination duty cycles. Measurement performance is evaluated over a range of illumination duty cycles, both for a standard range imaging camera configuration, and also using a more complicated phase encoding method that is designed to cancel aliased harmonics during the sampling process. The standard configuration benefits from improved measurement linearity for illumination duty cycles around 30%, while the measured amplitude, hence range precision, is increased for both methods as the duty cycle is reduced below 50% (while maintaining constant optical power).

year: 2011

title: IntCal13 and Marine13 radiocarbon age calibration curves 0-50,000 years cal BP

authors: Reimer, Paula J.

abstract: The IntCal09 and Marine09 radiocarbon calibration curves have been revised utilizing newly available and updated data sets from 14C measurements on tree rings, plant macrofossils, speleothems, corals, and foraminifera. The calibration curves were derived from the data using the random walk model (RWM) used to generate IntCal09 and Marine09, which has been revised to account for additional uncertainties and error structures. The new curves were ratified at the 21st International Radiocarbon conference in July 2012 and are available as Supplemental Material at www.radiocarbon.org. The database can be accessed at http://intcal.qub.ac.uk/intcal13/.

text: IntCal13 and Marine13 radiocarbon age calibration curves 0-50,000 years cal BP The IntCal09 and Marine09 radiocarbon calibration curves have been revised utilizing newly available and updated data sets from 14C measurements on tree rings, plant macrofossils, speleothems, corals, and foraminifera. The calibration curves were derived from the data using the random walk model (RWM) used to generate IntCal09 and Marine09, which has been revised to account for additional uncertainties and error structures. The new curves were ratified at the 21st International Radiocarbon conference in July 2012 and are available as Supplemental Material at www.radiocarbon.org. The database can be accessed at http://intcal.qub.ac.uk/intcal13/.

year: 2013

title: Mana motuhake ā-raraunga: datafication and social science research in Aotearoa

authors: Kukutai, Tahu

abstract: Social practices, interactions and relations are increasingly being turned into data, driven by technologies that enable new methods of data accumulation, digitisation, integration and manipulation (Taylor and Broeders 2015; Couldry and Yu 2018; Mann and Daly 2019). This ‘datafication’ is not only transforming social relations, it is also reshaping social science through the generation of datasets that open up new avenues for research and methodological development (van Dijck 2014) and generating debate about the relationships between data, digitalisation, ethics and human wellbeing (boyd and Crawford 2012; Mittelstadt and Floridi 2016; O’Neil 2016; Eubanks 2018).

text: Mana motuhake ā-raraunga: datafication and social science research in Aotearoa Social practices, interactions and relations are increasingly being turned into data, driven by technologies that enable new methods of data accumulation, digitisation, integration and manipulation (Taylor and Broeders 2015; Couldry and Yu 2018; Mann and Daly 2019). This ‘datafication’ is not only transforming social relations, it is also reshaping social science through the generation of datasets that open up new avenues for research and methodological development (van Dijck 2014) and generating debate about the relationships between data, digitalisation, ethics and human wellbeing (boyd and Crawford 2012; Mittelstadt and Floridi 2016; O’Neil 2016; Eubanks 2018).

year: 2019