The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Deqing Ren - One of the best experts on this subject based on the ideXlab platform.
-
Phase quantization study of spatial light modulator for extreme high contrast imaging
The Astrophysical Journal, 2016Co-Authors: Jiangpei Dou, Deqing RenAbstract:Direct imaging of exoplanets by reflected starlight is extremely challenging due to the large luminosity ratio to the primary star. Wave-front control is a critical technique to attenuate the speckle noise in order to achieve an extremely high contrast. We present a Phase quantization study of a spatial light modulator (SLM) for wave-front control to meet the contrast requirement of detection of a terrestrial planet in the habitable zone of a solar-type star. We perform the numerical simulation by employing the SLM with different Phase accuracy and actuator numbers,which are related to the achievable contrast. We use an optimization algorithm to solve the quantization problems that is matched to the controllable Phase Step of the SLM. Two optical configurations are discussed with the SLM located before and after the coronagraph focal plane mask. The simulation result has constrained the specification for SLM Phase accuracy in the above two optical configurations, which gives us a Phase accuracy of 0.4/1000 and 1/1000 waves to achieve a contrast of 10-10. Finally, we have demonstrated that an SLM with more actuators can deliver a competitive contrast performance on the order of 10-10 in comparison to that by using a deformable mirror.
-
Phase quantization study of spatial light modulator for extreme high contrast imaging
arXiv: Instrumentation and Methods for Astrophysics, 2016Co-Authors: Jiangpei Dou, Deqing RenAbstract:Direct imaging of exoplanets by reflected starlight is extremely challenging due to the large luminosity ratio to the primary star. Wave-front control is a critical technique to attenuate the speckle noise in order to achieve an extremely high contrast. We present a Phase quantization study of a spatial light modulator for wave front control to meet the contrast requirement of detection of a terrestrial planet in the habitable zone of a solar-type star. We perform the numerical simulation by employing the SLM with different Phase accuracy and actuator numbers, which are related to the achievable contrast. We use an optimization algorithm to solve the quantization problems that is matched to the controllable Phase Step of the SLM. Two optical configurations are discussed with the SLM located before and after the coronagraph focal plane mask. The simulation result has constrained the specification for SLM Phase accuracy in the above two optical configurations. Finally, we have demonstrated that a SLM with more actuators can deliver a competitive contrast performance to that by using a deformable mirror.
Jiangpei Dou - One of the best experts on this subject based on the ideXlab platform.
-
Phase quantization study of spatial light modulator for extreme high contrast imaging
The Astrophysical Journal, 2016Co-Authors: Jiangpei Dou, Deqing RenAbstract:Direct imaging of exoplanets by reflected starlight is extremely challenging due to the large luminosity ratio to the primary star. Wave-front control is a critical technique to attenuate the speckle noise in order to achieve an extremely high contrast. We present a Phase quantization study of a spatial light modulator (SLM) for wave-front control to meet the contrast requirement of detection of a terrestrial planet in the habitable zone of a solar-type star. We perform the numerical simulation by employing the SLM with different Phase accuracy and actuator numbers,which are related to the achievable contrast. We use an optimization algorithm to solve the quantization problems that is matched to the controllable Phase Step of the SLM. Two optical configurations are discussed with the SLM located before and after the coronagraph focal plane mask. The simulation result has constrained the specification for SLM Phase accuracy in the above two optical configurations, which gives us a Phase accuracy of 0.4/1000 and 1/1000 waves to achieve a contrast of 10-10. Finally, we have demonstrated that an SLM with more actuators can deliver a competitive contrast performance on the order of 10-10 in comparison to that by using a deformable mirror.
-
Phase quantization study of spatial light modulator for extreme high contrast imaging
arXiv: Instrumentation and Methods for Astrophysics, 2016Co-Authors: Jiangpei Dou, Deqing RenAbstract:Direct imaging of exoplanets by reflected starlight is extremely challenging due to the large luminosity ratio to the primary star. Wave-front control is a critical technique to attenuate the speckle noise in order to achieve an extremely high contrast. We present a Phase quantization study of a spatial light modulator for wave front control to meet the contrast requirement of detection of a terrestrial planet in the habitable zone of a solar-type star. We perform the numerical simulation by employing the SLM with different Phase accuracy and actuator numbers, which are related to the achievable contrast. We use an optimization algorithm to solve the quantization problems that is matched to the controllable Phase Step of the SLM. Two optical configurations are discussed with the SLM located before and after the coronagraph focal plane mask. The simulation result has constrained the specification for SLM Phase accuracy in the above two optical configurations. Finally, we have demonstrated that a SLM with more actuators can deliver a competitive contrast performance to that by using a deformable mirror.
Masoomeh Dashtdar - One of the best experts on this subject based on the ideXlab platform.
-
quantitative Phase imaging based on fresnel diffraction from a Phase plate
Applied Physics Letters, 2019Co-Authors: Samira Ebrahimi, Masoomeh DashtdarAbstract:The structural complexity and instability of many interference Phase microscopy methods are the major obstacles toward high-precision Phase measurement. In this vein, improving more efficient configurations as well as proposing methods are the subjects of growing interest. Here, we introduce Fresnel diffraction from a Phase Step to the realm of quantitative Phase imaging. By employing Fresnel diffraction of a divergent (or convergent) beam of light from a plane-parallel Phase plate, we provide a viable, simple, and compact platform for three-dimensional imaging of micrometer-sized specimens. The recorded diffraction pattern of the outgoing light from an imaging system in the vicinity of the plate edge can be served as a hologram, which would be analyzed via the Fourier transform method to measure the sample Phase information. The period of diffraction fringes is adjustable simply by rotating the plate without the reduction of both the field of view and fringe contrast. The high stability of the presented method is affirmatively confirmed through comparison of the result with that of the conventional Mach–Zehnder based digital holographic method. Quantitative Phase measurements on silica microspheres, onion skins, and red blood cells ensure the validity of the method and its ability for monitoring nanometer-scale fluctuations of living cells, particularly in real-time.The structural complexity and instability of many interference Phase microscopy methods are the major obstacles toward high-precision Phase measurement. In this vein, improving more efficient configurations as well as proposing methods are the subjects of growing interest. Here, we introduce Fresnel diffraction from a Phase Step to the realm of quantitative Phase imaging. By employing Fresnel diffraction of a divergent (or convergent) beam of light from a plane-parallel Phase plate, we provide a viable, simple, and compact platform for three-dimensional imaging of micrometer-sized specimens. The recorded diffraction pattern of the outgoing light from an imaging system in the vicinity of the plate edge can be served as a hologram, which would be analyzed via the Fourier transform method to measure the sample Phase information. The period of diffraction fringes is adjustable simply by rotating the plate without the reduction of both the field of view and fringe contrast. The high stability of the presented ...
-
quantitative Phase imaging based on fresnel diffraction from a Phase plate
arXiv: Optics, 2018Co-Authors: Samira Ebrahimi, Masoomeh DashtdarAbstract:The structural complexity and instability of many interference Phase microscopy methods are the major obstacles toward high-precision Phase measurement. In this vein, improving more efficient configurations as well as proposing new methods are the subjects of growing interest. Here we introduce Fresnel diffraction from a Phase Step to the realm of quantitative Phase imaging. By employing Fresnel diffraction of a divergent (or convergent) beam of light from a plane-parallel Phase plate, we provide a viable, simple and compact platform for three-dimensional imaging of micron-sized specimens. The recorded diffraction pattern of the outgoing light from an imaging system in the vicinity of the plate edge can be served as a hologram, which would be analyzed via Fourier transform method to measure the sample Phase information. The period of diffraction fringes is adjustable simply by rotating the plate without the reduction of both field of view and fringe contrast. The high stability of the presented method is affirmatively confirmed through comparison the result with that of conventional Mach-Zehnder based digital holographic method. Quantitative Phase measurements on silica microspheres, onion skin and red blood cells ensure the validity of the method and its ability for monitoring nanometer-scale fluctuations of living cells, particularly in real-time.
-
focal length measurement based on fresnel diffraction from a Phase plate
Applied Optics, 2016Co-Authors: Masoomeh Dashtdar, Mohammadali S HosseinisaberAbstract:A method based on the Fresnel diffraction of light from the Phase Step is introduced for measuring effective focal length (EFL) and back focal length (BFL) of optical imaging systems. It is shown that, as a transparent plane-parallel plate is illuminated at a boundary region by a monochromatic beam of light, Fresnel diffraction occurs because of the abrupt change in Phase imposed by the finite change in refractive index at the plate boundary. Variation of the incident angle in a convergent (or divergent) beam of light causes the periodic intensity along the central fringe of the diffraction pattern. The measurement of the extrema position of the intensity distribution accurately provides the EFL and BFL. The technique is easy to apply and can measure a wide range of both positive and negative focal lengths. The measuring setup can be very compact with low mechanical and optical noises. As examples of this technique, the EFLs of five different lenses are experimentally obtained. The results are quite consistent with the values indicated by the lens manufacturer.
A Bellini - One of the best experts on this subject based on the ideXlab platform.
-
3boost a high power three Phase Step up full bridge converter for automotive applications
IEEE Transactions on Industrial Electronics, 2008Co-Authors: G Franceschini, Emilio Lorenzani, M Cavatorta, A BelliniAbstract:This paper describes a simple dc-dc Step-up converter topology for switch-mode dc power supplies. The proposed configuration is well suited for high-power applications with battery supply. In the automotive framework, the push-pull architecture is the most widespread. However, as power increases, the use of a full-bridge architecture is mandatory. This paper presents a full-bridge architecture where the traditional single-Phase transformer is replaced by a three-Phase transformer. A prototype was realized and tested for the power supply of automotive devices. In this environment, one of the most important requirements is the ability to provide a burst of power during short-duration events, together with high-efficiency and high-quality output voltage. The latter constraints can be achieved by only using closed-loop switch-mode dc-dc converters at high switching frequency, thus reducing converter efficiency and creating electromagnetic-compatibility (EMC) problems. In this paper, the aforementioned issues were tackled relying on an open-loop topology. Open-loop converters are feasible if the output resistance of the converter is as low as possible, and a possible solution is the minimization of power losses. The solution is the use of a three-Phase transformer with a delta-wye connection within a full-bridge converter topology. The configuration will be referred to as 3boost power supply. The three-Phase transformer replaces the common single-Phase transformer, and it is driven by a three-Phase full-bridge inverter operating in six-Step modulation. At secondary, a three-Phase full wave diode rectifier is used to obtain the output dc voltage level. Therefore, a unitary transformer utilization factor is achieved. A simple theoretical comparison between the three types of converters-push-pull, conventional full bridge, and 3boost is shown. A low-power version of the converter was realized. Experiments confirm that this topology allows to achieve a high efficiency, a lower ripple factor, and a good EMC behavior.
-
3boost a high power three Phase Step up full bridge converter for automotive applications
Conference of the Industrial Electronics Society, 2004Co-Authors: G Franceschini, Emilio Lorenzani, M Cavatorta, A BelliniAbstract:This paper presents a simple and original DC/DC Step-up converter topology for switch-mode DC power supplies. The proposed architecture is well suited for high power applications with battery supply. A prototype was realized and tested for the power supply of automotive devices. In this environment signals are characterized by high dynamic variations, thus they can be operated only relying on power supplies with high dynamic capabilities. The latter constraint can be achieved only using closed-loop switch-mode DC/DC converters at high switching frequency. So doing converter efficiency is reduced, and EMC problems arise. In summary power supply efficiency and supply voltage quality are key features of the converter design. In this paper the above mentioned issued were tackled relying on an open loop topology. The original solution is the adoption of a three-Phase transformer with delta-wye connection within a full-bridge converter topology. The proposed architecture will be referred to as 3boost power supply. The three-Phase transformer replaces the common single-Phase transformer and it is supplied at primary by three square waves, produced by a three-Phase full bridge inverter. At secondary a three-Phase full wave diode rectifier is used to obtain the output DC voltage level. Experimental results confirm that this topology, with respect to a single-Phase push-pull converter, allows to achieve higher efficiency, a lower ripple factor, and a unitary transformer utilization factor. The proposed architecture is patent pending.
Geza Joos - One of the best experts on this subject based on the ideXlab platform.
-
wide frequency range adaptive phasor and frequency pmu algorithms
IEEE Transactions on Smart Grid, 2014Co-Authors: Innocent Kamwa, S R Samantaray, Geza JoosAbstract:The paper deals with developing and testing frequency-adaptive PMU algorithms with wider linearity range than specified in IEEE Std C37.118-1. This goal is achieved by means of three different concepts encompassing robust state-of-the-art design approaches: 1) FIR bandpass filtering, 2) extended Kalman filtering (EKF), and 3) discrete Fourier transform (DFT) demodulation with FIR low-pass smoothing. While FIR-based PMUs are linear Phase with no overshoot in either Phase or amplitude Step responses, the adaptive EKF PMU is more computer-intensive but allows for a reduced group delay and better out-of-band interference rejection at the cost of a Phase Step response with overshoot. Frequency measurement performances of the various PMUs are assessed in detail. It turned out that FIR PMUs are best for meeting Std C37-118-1 metrics but they are outperformed by EKF under changing harmonics. Test results on three recent commercial PMU models further confirm that PMU algorithms meeting standard C37-118-1 can behave quite differently under dynamic conditions.
-
compliance analysis of pmu algorithms and devices for wide area stabilizing control of large power systems
IEEE Transactions on Power Systems, 2013Co-Authors: Innocent Kamwa, S R Samantaray, Geza JoosAbstract:For the first time, IEEE Std. C37.118.1-2011 now provides metrics for PMU dynamic performance in terms of classes P and M filter designs. This paper attempts to determine whether fulfilling these requirements makes the PMU inherently well suited for stability control applications such as wide-area power system stabilizers (PSSs). In this aim, we considered two different frequency-adaptive approaches for class-P and -M compliance to ensure operation over a wide frequency range. The first is based on a finite-impulse response (FIR) with no overshoot in either the Phase or the amplitude Step responses, while the second is Kalman filter-based (EKF), which allows for a more refined out-of-band interference rejection at the cost of a Phase Step response with overshoot. These two approaches are benchmarked against Hydro-Quebec`s existing PSS requirements and the conclusion is that the total vector error-based response time is not indicative of the Phase lag within the frequency band of interest, nor of the 3-dB bandwidth under sinusoidal amplitude/frequency modulation phenomena, which are key criteria when specifying PSS PMUs. Using simulated and field-recorded network fault responses, we also show that a class-M PMU is unsatisfactory for wide-area stabilizing control, unless its performance is improved during the fault period, which is not covered by Std. C37.118.1-2011.