title: Toward-1mm depth precision with a solid state full-field range imaging system

authors: Dorrington, Adrian A.

subjects: solid-state

abstract: Previously, we demonstrated a novel heterodyne based solid-state full-field range-finding imaging system. This system is comprised of modulated LED illumination, a modulated image intensifier, and a digital video camera. A 10 MHz drive is provided with 1 Hz difference between the LEDs and image intensifier. A sequence of images of the resulting beating intensifier output are captured and processed to determine phase and hence distance to the object for each pixel. In a previous publication, we detailed results showing a one-sigma precision of 15 mm to 30 mm (depending on signal strength). Furthermore, we identified the limitations of the system and potential improvements that were expected to result in a range precision in the order of 1 mm. These primarily include increasing the operating frequency and improving optical coupling and sensitivity. In this paper, we report on the implementation of these improvements and the new system characteristics. We also comment on the factors that are important for high precision image ranging and present configuration strategies for best performance. Ranging with sub-millimeter precision is demonstrated by imaging a planar surface and calculating the deviations from a planar fit. The results are also illustrated graphically by imaging a garden gnome.

text: Toward-1mm depth precision with a solid state full-field range imaging system Previously, we demonstrated a novel heterodyne based solid-state full-field range-finding imaging system. This system is comprised of modulated LED illumination, a modulated image intensifier, and a digital video camera. A 10 MHz drive is provided with 1 Hz difference between the LEDs and image intensifier. A sequence of images of the resulting beating intensifier output are captured and processed to determine phase and hence distance to the object for each pixel. In a previous publication, we detailed results showing a one-sigma precision of 15 mm to 30 mm (depending on signal strength). Furthermore, we identified the limitations of the system and potential improvements that were expected to result in a range precision in the order of 1 mm. These primarily include increasing the operating frequency and improving optical coupling and sensitivity. In this paper, we report on the implementation of these improvements and the new system characteristics. We also comment on the factors that are important for high precision image ranging and present configuration strategies for best performance. Ranging with sub-millimeter precision is demonstrated by imaging a planar surface and calculating the deviations from a planar fit. The results are also illustrated graphically by imaging a garden gnome.

year: 2006

title: Synthesis and properties of some doped lithium transition-metal phosphates

authors: Butt, Garrett Phillip

abstract: Four structurally related materials; LiNiPO₄, LiCoPO₄, Li₃Fe₂(PO₄)₃ and Li₃V₂(PO₄)₃, were synthesised, characterised and evaluated as potential cathode materials for lithium secondary batteries. 

The materials were synthesized using mainly solid-state techniques. Structural characterisation was performed using powder XRD with Rietveld refinement and Raman spectroscopy. Results showed that the pure forms of LiNiPO₄, LiCoPO₄ and Li₃Fe₂(PO₄)₃ could be synthesised in air at various temperatures. Li₃V₂(PO₄)₃ required a reducing atmosphere of 2%H₂/98%N₂ to achieve phase purity. Attempts were made to substitute all four materials with aliovalent dopants. Li₃Fe₂(PO₄)₃ and Li₃V₂(PO₄)₃ underwent a phase change depending on dopant content to a higher ionic conducting phase. 

AC impedance spectroscopy was used to determine conductivity of the materials. In general the phosphates are poor conductors. There was a significant increase in conductivity when substituting the transition metal Ti⁴⁺ for M³⁺ in Li₃Fe₂(PO₄)₃ and Li₃V₂(PO₄)₃, and V³⁺ for Co²⁺ in LiCoPO₄. 

The four materials and their highest conducting doped analogues were evaluated as cathodes in coin type lithium cells to determine their viability in Li secondary batteries. LiCoPO₄ showed a first discharge capacity of 130 mAh/g at 4.6V, but could be cycled over only a limited number of charge-discharge cycles owing to electrolyte instability at the high oxidation potentials (>5V) required for full charge. LiNiPO₄ could not be charged at all to accessible voltages. Ti doped Li₃Fe₂(PO₄)₃ had a relatively low discharge capacity of 60 mAh/g. Li₃V₂(PO₄)₃ and Ti doped Li₃V₂(PO₄)₃ showed a discharge capacity of 130 and 110 mAh/g respectively, although the Ti doped Li₃V₂(PO₄)₃ showed better cycling characteristics. Therefore, although aliovalent doping could increase the total conductivity of the phosphate materials, the accessible capacities of these materials remained limited.

text: Synthesis and properties of some doped lithium transition-metal phosphates Four structurally related materials; LiNiPO₄, LiCoPO₄, Li₃Fe₂(PO₄)₃ and Li₃V₂(PO₄)₃, were synthesised, characterised and evaluated as potential cathode materials for lithium secondary batteries. 

The materials were synthesized using mainly solid-state techniques. Structural characterisation was performed using powder XRD with Rietveld refinement and Raman spectroscopy. Results showed that the pure forms of LiNiPO₄, LiCoPO₄ and Li₃Fe₂(PO₄)₃ could be synthesised in air at various temperatures. Li₃V₂(PO₄)₃ required a reducing atmosphere of 2%H₂/98%N₂ to achieve phase purity. Attempts were made to substitute all four materials with aliovalent dopants. Li₃Fe₂(PO₄)₃ and Li₃V₂(PO₄)₃ underwent a phase change depending on dopant content to a higher ionic conducting phase. 

AC impedance spectroscopy was used to determine conductivity of the materials. In general the phosphates are poor conductors. There was a significant increase in conductivity when substituting the transition metal Ti⁴⁺ for M³⁺ in Li₃Fe₂(PO₄)₃ and Li₃V₂(PO₄)₃, and V³⁺ for Co²⁺ in LiCoPO₄. 

The four materials and their highest conducting doped analogues were evaluated as cathodes in coin type lithium cells to determine their viability in Li secondary batteries. LiCoPO₄ showed a first discharge capacity of 130 mAh/g at 4.6V, but could be cycled over only a limited number of charge-discharge cycles owing to electrolyte instability at the high oxidation potentials (>5V) required for full charge. LiNiPO₄ could not be charged at all to accessible voltages. Ti doped Li₃Fe₂(PO₄)₃ had a relatively low discharge capacity of 60 mAh/g. Li₃V₂(PO₄)₃ and Ti doped Li₃V₂(PO₄)₃ showed a discharge capacity of 130 and 110 mAh/g respectively, although the Ti doped Li₃V₂(PO₄)₃ showed better cycling characteristics. Therefore, although aliovalent doping could increase the total conductivity of the phosphate materials, the accessible capacities of these materials remained limited.

year: 2000

title: Place imaginaries: Photography and place-making at Te Awa River Ride

authors: Hill, Rodrigo

subjects: photography

abstract: Contemporary photographic practice has evolved into a field of possibilities, which includes a flux of representational modes that depict experiences, feelings and emotions. This PhD with Creative Practice Components investigates how photography is embedded within ways of knowing, experiencing and making places and the subsequent visual constructions of place imaginaries.  Drawing on contemporary photographic practice and theory, I position myself as a qualitative researcher engaged in creative practice, specifically lens-based approaches and modes of photographic representation. In contrast to photography’s dominant discourse centred on indexical and objective assumptions, I understand photographic practices and images as constructions of multiple meanings.

I use Te Awa River Ride as my research locale, a place where different practices and discourses entangle, forming a diverse set of dynamic and intersecting meanings. Te Awa River Ride is a shared pathway, with a planned total length of 70 kilometres, that edges the banks of the Waikato River from Ngāruawāhia to Cambridge, in the central North Island of Aotearoa New Zealand. I understand Te Awa River Ride as a place-composite, layered by multiple place imaginaries, including indigenous Māori, Pākehā and European ways of meaning and place-making. In this thesis I draw upon place imaginaries as a way of expressing visual possibilities, constructions and affective responses to my own and others’ experiences at this unique research location. 

My photography practice aims to actualise particular place imaginaries through curation and sequencing of lens-based explorations of light, movement and water. This process and the compilation of imagery into curatorial products, such as photography installations, generate novel ways of perceiving the Waikato River and Te Awa River Ride, revealing the centrality of photography in place-making processes.

text: Place imaginaries: Photography and place-making at Te Awa River Ride Contemporary photographic practice has evolved into a field of possibilities, which includes a flux of representational modes that depict experiences, feelings and emotions. This PhD with Creative Practice Components investigates how photography is embedded within ways of knowing, experiencing and making places and the subsequent visual constructions of place imaginaries.  Drawing on contemporary photographic practice and theory, I position myself as a qualitative researcher engaged in creative practice, specifically lens-based approaches and modes of photographic representation. In contrast to photography’s dominant discourse centred on indexical and objective assumptions, I understand photographic practices and images as constructions of multiple meanings.

I use Te Awa River Ride as my research locale, a place where different practices and discourses entangle, forming a diverse set of dynamic and intersecting meanings. Te Awa River Ride is a shared pathway, with a planned total length of 70 kilometres, that edges the banks of the Waikato River from Ngāruawāhia to Cambridge, in the central North Island of Aotearoa New Zealand. I understand Te Awa River Ride as a place-composite, layered by multiple place imaginaries, including indigenous Māori, Pākehā and European ways of meaning and place-making. In this thesis I draw upon place imaginaries as a way of expressing visual possibilities, constructions and affective responses to my own and others’ experiences at this unique research location. 

My photography practice aims to actualise particular place imaginaries through curation and sequencing of lens-based explorations of light, movement and water. This process and the compilation of imagery into curatorial products, such as photography installations, generate novel ways of perceiving the Waikato River and Te Awa River Ride, revealing the centrality of photography in place-making processes.

year: 2019