11,798 research outputs found
Tailoring a coherent control solution landscape by linear transforms of spectral phase basis
Finding an optimal phase pattern in a multidimensional solution landscape becomes easier and faster if local optima are suppressed and contour lines are tailored towards closed convex patterns. Using wideband second harmonic generation as a coherent control test case, we show that a linear combination of spectral phase basis functions can result in such improvements and also in separable phase terms, each of which can be found independently. The improved shapes are attributed to a suppressed nonlinear shear, changing the relative orientation of contour lines. The first order approximation of the process shows a simple relation between input and output phase profiles, useful for pulse shaping at ultraviolet wavelengths
Active vision for dexterous grasping of novel objects
How should a robot direct active vision so as to ensure reliable grasping? We
answer this question for the case of dexterous grasping of unfamiliar objects.
By dexterous grasping we simply mean grasping by any hand with more than two
fingers, such that the robot has some choice about where to place each finger.
Such grasps typically fail in one of two ways, either unmodeled objects in the
scene cause collisions or object reconstruction is insufficient to ensure that
the grasp points provide a stable force closure. These problems can be solved
more easily if active sensing is guided by the anticipated actions. Our
approach has three stages. First, we take a single view and generate candidate
grasps from the resulting partial object reconstruction. Second, we drive the
active vision approach to maximise surface reconstruction quality around the
planned contact points. During this phase, the anticipated grasp is continually
refined. Third, we direct gaze to improve the safety of the planned reach to
grasp trajectory. We show, on a dexterous manipulator with a camera on the
wrist, that our approach (80.4% success rate) outperforms a randomised
algorithm (64.3% success rate).Comment: IROS 2016. Supplementary video: https://youtu.be/uBSOO6tMzw
Inverse scattering for reflection intensity phase microscopy
Reflection phase imaging provides label-free, high-resolution characterization of biological samples, typically using interferometric-based techniques. Here, we investigate reflection phase microscopy from intensity-only measurements under diverse illumination. We evaluate the forward and inverse scattering model based on the first Born approximation for imaging scattering objects above a glass slide. Under this design, the measured field combines linear forward-scattering and height-dependent nonlinear back-scattering from the object that complicates object phase recovery. Using only the forward-scattering, we derive a linear inverse scattering model and evaluate this model's validity range in simulation and experiment using a standard reflection microscope modified with a programmable light source. Our method provides enhanced contrast of thin, weakly scattering samples that complement transmission techniques. This model provides a promising development for creating simplified intensity-based reflection quantitative phase imaging systems easily adoptable for biological research.https://arxiv.org/abs/1912.07709Accepted manuscrip
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