title: Development of a Full-Field Time-of-Flight Range Imaging System

authors: Payne, Andrew D.

subjects: Range Imaging

abstract: A full-field, time-of-flight, image ranging system or  3D camera  has been developed from a proof-of-principle to a working prototype stage, capable of determining the intensity and range for every pixel in a scene. The system can be adapted to the requirements of various applications, producing high precision range measurements with sub-millimetre resolution, or high speed measurements at video frame rates. Parallel data acquisition at each pixel provides high spatial resolution independent of the operating speed.
The range imaging system uses a heterodyne technique to indirectly measure time of flight. Laser diodes with highly diverging beams are intensity modulated at radio frequencies and used to illuminate the scene. Reflected light is focused on to an image intensifier used as a high speed optical shutter, which is modulated at a slightly different frequency to that of the laser source. The output from the shutter is a low frequency beat signal, which is sampled by a digital video camera. Optical propagation delay is encoded into the phase of the beat signal, hence from a captured time variant intensity sequence, the beat signal phase can be measured to determine range for every pixel in the scene.
A direct digital synthesiser (DDS) is designed and constructed, capable of generating up to three outputs at frequencies beyond 100 MHz with the relative frequency stability in excess of nine orders of magnitude required to control the laser and shutter modulation. Driver circuits were also designed to modulate the image intensifier photocathode at 50 Vpp, and four laser diodes with a combined power output of 320 mW, both over a frequency range of 10-100 MHz. The DDS, laser, and image intensifier response are characterised. A unique method of measuring the image intensifier optical modulation response is developed, requiring the construction of a pico-second pulsed laser source.
This characterisation revealed deficiencies in the measured responses, which were mitigated through hardware modifications where possible. The effects of remaining imperfections, such as modulation waveform harmonics and image intensifier irising, can be calibrated and removed from the range measurements during software processing using the characterisation data. 
Finally, a digital method of generating the high frequency modulation signals using a FPGA to replace the analogue DDS is developed, providing a highly integrated solution, reducing the complexity, and enhancing flexibility. In addition, a novel modulation coding technique is developed to remove the undesirable influence of waveform harmonics from the range measurement without extending the acquisition time. When combined with a proposed modification to the laser illumination source, the digital system can enhance range measurement precision and linearity.
From this work, a flexible full-field image ranging system is successfully realised. The system is demonstrated operating in a high precision mode with sub-millimetre depth resolution, and also in a high speed mode operating at video update rates (25 fps), in both cases providing high (512 512) spatial resolution over distances of several metres.

text: Development of a Full-Field Time-of-Flight Range Imaging System A full-field, time-of-flight, image ranging system or  3D camera  has been developed from a proof-of-principle to a working prototype stage, capable of determining the intensity and range for every pixel in a scene. The system can be adapted to the requirements of various applications, producing high precision range measurements with sub-millimetre resolution, or high speed measurements at video frame rates. Parallel data acquisition at each pixel provides high spatial resolution independent of the operating speed.
The range imaging system uses a heterodyne technique to indirectly measure time of flight. Laser diodes with highly diverging beams are intensity modulated at radio frequencies and used to illuminate the scene. Reflected light is focused on to an image intensifier used as a high speed optical shutter, which is modulated at a slightly different frequency to that of the laser source. The output from the shutter is a low frequency beat signal, which is sampled by a digital video camera. Optical propagation delay is encoded into the phase of the beat signal, hence from a captured time variant intensity sequence, the beat signal phase can be measured to determine range for every pixel in the scene.
A direct digital synthesiser (DDS) is designed and constructed, capable of generating up to three outputs at frequencies beyond 100 MHz with the relative frequency stability in excess of nine orders of magnitude required to control the laser and shutter modulation. Driver circuits were also designed to modulate the image intensifier photocathode at 50 Vpp, and four laser diodes with a combined power output of 320 mW, both over a frequency range of 10-100 MHz. The DDS, laser, and image intensifier response are characterised. A unique method of measuring the image intensifier optical modulation response is developed, requiring the construction of a pico-second pulsed laser source.
This characterisation revealed deficiencies in the measured responses, which were mitigated through hardware modifications where possible. The effects of remaining imperfections, such as modulation waveform harmonics and image intensifier irising, can be calibrated and removed from the range measurements during software processing using the characterisation data. 
Finally, a digital method of generating the high frequency modulation signals using a FPGA to replace the analogue DDS is developed, providing a highly integrated solution, reducing the complexity, and enhancing flexibility. In addition, a novel modulation coding technique is developed to remove the undesirable influence of waveform harmonics from the range measurement without extending the acquisition time. When combined with a proposed modification to the laser illumination source, the digital system can enhance range measurement precision and linearity.
From this work, a flexible full-field image ranging system is successfully realised. The system is demonstrated operating in a high precision mode with sub-millimetre depth resolution, and also in a high speed mode operating at video update rates (25 fps), in both cases providing high (512 512) spatial resolution over distances of several metres.

year: 2008

title: An Examination of the Noken and Indigenous Cultural Identity: Voices of Papuan Women

authors: Kanem, Veronika

subjects: cultural identity

abstract: Noken is an essential tool/bag/clothing in the lives of Indigenous people of West Papua, which is made from knitting thin strips of wood primarily from the Gnetum Gnemon tree. Raw materials required to make noken have become scarce due to massive deforestation. An analysis of the noken lends itself to a useful understanding of the link between economic development initiatives in the Merauke Regency of West Papua and shifting cultural identity among Indigenous Papuans. Drawing on the Women, Culture and Development (WCD) approach, this qualitative study examines interviews from Papuan women in order to understand how the noken resonates with Indigenous Papuans, and how perceptions of noken and their accessibility have changed. The findings reveal that a combination of factors contribute to dwindling noken supplies, which adversely impact Papuans’ ability to produce and reproduce their culture. This paper argues that Papuan women possess an unwritten specialized knowledge that is of increased value in a shifting social context and hold new meaning in response to competing influences of non-Papuans.

text: An Examination of the Noken and Indigenous Cultural Identity: Voices of Papuan Women Noken is an essential tool/bag/clothing in the lives of Indigenous people of West Papua, which is made from knitting thin strips of wood primarily from the Gnetum Gnemon tree. Raw materials required to make noken have become scarce due to massive deforestation. An analysis of the noken lends itself to a useful understanding of the link between economic development initiatives in the Merauke Regency of West Papua and shifting cultural identity among Indigenous Papuans. Drawing on the Women, Culture and Development (WCD) approach, this qualitative study examines interviews from Papuan women in order to understand how the noken resonates with Indigenous Papuans, and how perceptions of noken and their accessibility have changed. The findings reveal that a combination of factors contribute to dwindling noken supplies, which adversely impact Papuans’ ability to produce and reproduce their culture. This paper argues that Papuan women possess an unwritten specialized knowledge that is of increased value in a shifting social context and hold new meaning in response to competing influences of non-Papuans.

year: 2018

title: Hā Ora: Reflecting on a Kaupapa Māori community engaged co-design approach to lung cancer research

authors: Kidd, Jacquie

abstract: Co-designed research is gaining prominence within the health care space. Community engagement is a key premise of co-design and is also particularly vital when carrying out kaupapa Māori research. Kaupapa Māori describes a “by Māori, for Māori” approach to research in Aotearoa/New Zealand. This article discusses the research process of Hā Ora: a co-design project underpinned by a kaupapa Māori approach. The objective was to explore the barriers to early presentation and diagnosis of lung cancer, barriers identified by Māori. The team worked with four rural Māori communities, with whom we aimed to co-design local interventions that would promote earlier diagnosis of lung cancer. This article highlights and unpacks the complexities of carrying out community- engaged co-design with Māori who live in rural communities. In particular, we draw attention to the importance of flexibility and adaptability in the research process. We highlight issues pertaining to timelines and budgets, and also the intricacies of involving co-governance and advisory groups. Overall, through this article, we argue that health researchers need to prioritise working with and for participants, rather than on them, especially when working with Māori communities.

text: Hā Ora: Reflecting on a Kaupapa Māori community engaged co-design approach to lung cancer research Co-designed research is gaining prominence within the health care space. Community engagement is a key premise of co-design and is also particularly vital when carrying out kaupapa Māori research. Kaupapa Māori describes a “by Māori, for Māori” approach to research in Aotearoa/New Zealand. This article discusses the research process of Hā Ora: a co-design project underpinned by a kaupapa Māori approach. The objective was to explore the barriers to early presentation and diagnosis of lung cancer, barriers identified by Māori. The team worked with four rural Māori communities, with whom we aimed to co-design local interventions that would promote earlier diagnosis of lung cancer. This article highlights and unpacks the complexities of carrying out community- engaged co-design with Māori who live in rural communities. In particular, we draw attention to the importance of flexibility and adaptability in the research process. We highlight issues pertaining to timelines and budgets, and also the intricacies of involving co-governance and advisory groups. Overall, through this article, we argue that health researchers need to prioritise working with and for participants, rather than on them, especially when working with Māori communities.

year: 2021