Udumbara Wijesinghe - Academia.edu (original) (raw)
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Papers by Udumbara Wijesinghe
Sensors, Mar 24, 2020
Sensors that remotely track the displacement of a moving object have a wide range of applications... more Sensors that remotely track the displacement of a moving object have a wide range of applications from robotic control to motion capture. In this paper, we introduce a simple, small silicon integrated circuit sensor that tracks the angular displacement of an object tagged with a small light source, such as a light-emitting diode (LED). This sensor uses a new angular transduction mechanism, differential diffusion of photoelectrons generated from the light spot cast by the light tag onto a Si anode, that is described by a simple physics model using pinhole optics and carrier diffusion. Because the light spot is formed by a pinhole aperture integrated on the sensor chip, no external focusing optics are needed, reducing system complexity, size, and weight. Prototype sensors based on this model were fabricated and their basic characteristics are presented. These sensors transduce angular displacement of an LED across orthogonal latitudinal and longitudinal arcs into normalized differential photocathode currents with signal linearly proportional to LED angular position across a ± 40 • field-of-view. These sensors offer potential performance and ease-of-use benefits compared to existing displacement sensor technologies.
arXiv (Cornell University), Oct 4, 2017
Spin coating technique was used to synthesize pure ZnO and Cu doped ZnO films on amorphous and co... more Spin coating technique was used to synthesize pure ZnO and Cu doped ZnO films on amorphous and conducting glass substrates. The doped amount of Cu in ZnO was varied up to 5% in atomic percentage. Speed of spin coating system, coating time, initial chemical solution and annealing conditions were varied to optimize the properties of samples. Transmittance of samples was measured for ZnO doped with 1, 2, 3, 4 and 5% of Cu. Absorbance, reflectance and refractive index were
Thin films of undoped and Cu doped ZnO have been synthesized on amorphous and conducting glass su... more Thin films of undoped and Cu doped ZnO have been synthesized on amorphous and conducting glass substrates using spin coating technique. The doped amount of Cu in ZnO was varied up to 5% in atomic percentage. Speed of spin coating system, coating time, initial chemical solution and annealing conditions were varied to optimize the properties of samples. Transmittance of samples was measured for ZnO doped with 1, 2, 3, 4 and 5% of Cu. Absorbance, reflectance and refractive index were derived from the measured transmittance. Film thickness of each film was calculated using the graphs of refractive index versus wavelength. Film thickness varies in a random manner depending on the amount of ZnO or Cu doped ZnO solutions spread on the substrate. The energy gap of each film was calculated using the graph of square of absorption coefficient time photon energy versus photon energy. The calculated energy gap values of Cu doped ZnO film samples decrease with the Cu concentration in ZnO. This me...
arXiv: Applied Physics, 2017
Spin coating technique was used to synthesize pure ZnO and Cu doped ZnO films on amorphous and co... more Spin coating technique was used to synthesize pure ZnO and Cu doped ZnO films on amorphous and conducting glass substrates. The doped amount of Cu in ZnO was varied up to 5% in atomic percentage. Speed of spin coating system, coating time, initial chemical solution and annealing conditions were varied to optimize the properties of samples. Transmittance of samples was measured for ZnO doped with 1, 2, 3, 4 and 5% of Cu. Absorbance, reflectance and refractive index were derived from the measured transmittance. Film thickness of each film was calculated using the graphs of refractive index versus wavelength. Film thickness varies in a random manner depending on the amount of ZnO or Cu doped ZnO solutions spread on the substrate. The energy gap of each film was calculated using the graph of square of absorption coefficient time photon energy versus photon energy. The calculated energy gap values of Cu doped ZnO film samples decrease with the Cu concentration in ZnO. This means that the...
Cu doped transparent ZnO thin films were spin coated on conductive glass substrates. The samples ... more Cu doped transparent ZnO thin films were spin coated on conductive glass substrates. The samples were subsequently annealed in air for 1 hour at 500 0C in order to form the phase of ZnO. ZnO samples were doped with different Cu molar percentages up to 5%. The impedance and photovoltaic properties of sample were measured. Photocurrent and photovoltage of doped and undoped samples were measured in KI/I2 electrolyte. Adding a trace amount of Cu improved the conducting properties of ZnO samples without changing other basic properties of ZnO. The photocurrent gradually increases with the doping concentration due to the high conducting properties of Cu. Investigation was carried out only up to the doping concentration of 5%, because higher doping concentrations may significantly influence the other properties of ZnO such as transparence of the film. Impedance of samples was determined by fitting the data to an equivalent circuit. The impedance reaches the maximum value at Cu concentration...
Sensors, 2020
Sensors that remotely track the displacement of a moving object have a wide range of applications... more Sensors that remotely track the displacement of a moving object have a wide range of applications from robotic control to motion capture. In this paper, we introduce a simple, small silicon integrated circuit sensor that tracks the angular displacement of an object tagged with a small light source, such as a light-emitting diode (LED). This sensor uses a new angular transduction mechanism, differential diffusion of photoelectrons generated from the light spot cast by the light tag onto a Si anode, that is described by a simple physics model using pinhole optics and carrier diffusion. Because the light spot is formed by a pinhole aperture integrated on the sensor chip, no external focusing optics are needed, reducing system complexity, size, and weight. Prototype sensors based on this model were fabricated and their basic characteristics are presented. These sensors transduce angular displacement of an LED across orthogonal latitudinal and longitudinal arcs into normalized differenti...
IEEE Sensors Journal, 2022
Applied Physics Letters, 2017
Sensors, Mar 24, 2020
Sensors that remotely track the displacement of a moving object have a wide range of applications... more Sensors that remotely track the displacement of a moving object have a wide range of applications from robotic control to motion capture. In this paper, we introduce a simple, small silicon integrated circuit sensor that tracks the angular displacement of an object tagged with a small light source, such as a light-emitting diode (LED). This sensor uses a new angular transduction mechanism, differential diffusion of photoelectrons generated from the light spot cast by the light tag onto a Si anode, that is described by a simple physics model using pinhole optics and carrier diffusion. Because the light spot is formed by a pinhole aperture integrated on the sensor chip, no external focusing optics are needed, reducing system complexity, size, and weight. Prototype sensors based on this model were fabricated and their basic characteristics are presented. These sensors transduce angular displacement of an LED across orthogonal latitudinal and longitudinal arcs into normalized differential photocathode currents with signal linearly proportional to LED angular position across a ± 40 • field-of-view. These sensors offer potential performance and ease-of-use benefits compared to existing displacement sensor technologies.
arXiv (Cornell University), Oct 4, 2017
Spin coating technique was used to synthesize pure ZnO and Cu doped ZnO films on amorphous and co... more Spin coating technique was used to synthesize pure ZnO and Cu doped ZnO films on amorphous and conducting glass substrates. The doped amount of Cu in ZnO was varied up to 5% in atomic percentage. Speed of spin coating system, coating time, initial chemical solution and annealing conditions were varied to optimize the properties of samples. Transmittance of samples was measured for ZnO doped with 1, 2, 3, 4 and 5% of Cu. Absorbance, reflectance and refractive index were
Thin films of undoped and Cu doped ZnO have been synthesized on amorphous and conducting glass su... more Thin films of undoped and Cu doped ZnO have been synthesized on amorphous and conducting glass substrates using spin coating technique. The doped amount of Cu in ZnO was varied up to 5% in atomic percentage. Speed of spin coating system, coating time, initial chemical solution and annealing conditions were varied to optimize the properties of samples. Transmittance of samples was measured for ZnO doped with 1, 2, 3, 4 and 5% of Cu. Absorbance, reflectance and refractive index were derived from the measured transmittance. Film thickness of each film was calculated using the graphs of refractive index versus wavelength. Film thickness varies in a random manner depending on the amount of ZnO or Cu doped ZnO solutions spread on the substrate. The energy gap of each film was calculated using the graph of square of absorption coefficient time photon energy versus photon energy. The calculated energy gap values of Cu doped ZnO film samples decrease with the Cu concentration in ZnO. This me...
arXiv: Applied Physics, 2017
Spin coating technique was used to synthesize pure ZnO and Cu doped ZnO films on amorphous and co... more Spin coating technique was used to synthesize pure ZnO and Cu doped ZnO films on amorphous and conducting glass substrates. The doped amount of Cu in ZnO was varied up to 5% in atomic percentage. Speed of spin coating system, coating time, initial chemical solution and annealing conditions were varied to optimize the properties of samples. Transmittance of samples was measured for ZnO doped with 1, 2, 3, 4 and 5% of Cu. Absorbance, reflectance and refractive index were derived from the measured transmittance. Film thickness of each film was calculated using the graphs of refractive index versus wavelength. Film thickness varies in a random manner depending on the amount of ZnO or Cu doped ZnO solutions spread on the substrate. The energy gap of each film was calculated using the graph of square of absorption coefficient time photon energy versus photon energy. The calculated energy gap values of Cu doped ZnO film samples decrease with the Cu concentration in ZnO. This means that the...
Cu doped transparent ZnO thin films were spin coated on conductive glass substrates. The samples ... more Cu doped transparent ZnO thin films were spin coated on conductive glass substrates. The samples were subsequently annealed in air for 1 hour at 500 0C in order to form the phase of ZnO. ZnO samples were doped with different Cu molar percentages up to 5%. The impedance and photovoltaic properties of sample were measured. Photocurrent and photovoltage of doped and undoped samples were measured in KI/I2 electrolyte. Adding a trace amount of Cu improved the conducting properties of ZnO samples without changing other basic properties of ZnO. The photocurrent gradually increases with the doping concentration due to the high conducting properties of Cu. Investigation was carried out only up to the doping concentration of 5%, because higher doping concentrations may significantly influence the other properties of ZnO such as transparence of the film. Impedance of samples was determined by fitting the data to an equivalent circuit. The impedance reaches the maximum value at Cu concentration...
Sensors, 2020
Sensors that remotely track the displacement of a moving object have a wide range of applications... more Sensors that remotely track the displacement of a moving object have a wide range of applications from robotic control to motion capture. In this paper, we introduce a simple, small silicon integrated circuit sensor that tracks the angular displacement of an object tagged with a small light source, such as a light-emitting diode (LED). This sensor uses a new angular transduction mechanism, differential diffusion of photoelectrons generated from the light spot cast by the light tag onto a Si anode, that is described by a simple physics model using pinhole optics and carrier diffusion. Because the light spot is formed by a pinhole aperture integrated on the sensor chip, no external focusing optics are needed, reducing system complexity, size, and weight. Prototype sensors based on this model were fabricated and their basic characteristics are presented. These sensors transduce angular displacement of an LED across orthogonal latitudinal and longitudinal arcs into normalized differenti...
IEEE Sensors Journal, 2022
Applied Physics Letters, 2017