Effect of optical aberrations on the color appearance of small defocused lights

We investigated influences of optics and surround area on color appearance of defocused, small narrow band photopic lights (1’ arc diameter, λmax 510 - 628 nm) centered within a black annulus and surrounded by a white field. Participants included seven normal trichromats with L- or M-cone biased ratios. We controlled chromatic aberration with elements of a Powell achromatizing lens and corrected higher-order aberrations with an adaptive-optics system. Longitudinal chromatic aberrations, but not monochromatic aberrations, are involved in changing appearance of small lights with defocus. Surround field structure is important because color changes were not observed when lights were presented on a uniform white surround

Changes in through-focus spatial visual performance with adaptive optics correction of monochromatic aberrations

We determined the influence of adaptive optics correction on through-focus illiterate-E visual acuity and through-focus contrast sensitivity under monochromatic conditions. In two subjects, adaptive optics improved high and low (12 %) contrast in-focus visual acuity by 0.1 to 0.15 logMAR, but resulted in more rapid and more symmetrical deterioration in visual acuity away from in-focus. In one subject, adaptive optics improved in-focus contrast sensitivity and resulted in more symmetrical and greater loss of contrast sensitivity about the peak sensitivity because of correction of higher order aberrations. The results show that full correction of higher order aberrations may worsen spatial visual performance in the presence of some defocus

Adaptive finite-time tracking control for robotic manipulators with funnel boundary

The finite-time tracking control problem with the output-constraint property of robotic manipulators subjected to system uncertainties is addressed. Specifically, the radial basis function neural network is employed to compensate for system uncertainties. The finite-time stability theorem is used for the backstepping design process, by which the limit of the settling time is set. A funnel boundary is used to limit the output overshoot. The proposed controller guarantees that all the signals are semi-globally practically finite-time bounded, while the tracking errors are enveloped by the funnel boundary. The performance of the proposed control method is illustrated by a numerical simulation of a 3-DOF manipulator. It is shown that the tracking errors are bounded by prescribed funnel boundaries. In the meantime, the manipulator is stabilized within a finite period of time

Fuzzy Finite-Time Tracking Control for a Class of Nonaffine Nonlinear Systems With Unknown Dead Zones

This paper addresses the finite-time tracking control problem for a class of nonaffine nonlinear systems with unknown dead zones using an adaptive fuzzy control scheme. The unknown nonlinear functions of the system are approximated by the fuzzy logic systems and a finite-time stability theorem is used to construct the control signal. The novelty of the proposed control method is that the tracking system can reach the stable equilibrium within a finite period of time without the knowledge of the bound

Manipulation of Molecular Vibrations on Condensing Er³⁺State Densities for 1.5 μm Application

Vibrational modes of chemical bonds in organic erbium (Er3+) materials play an important role in determining the efficiency of the 1.5 μm Er3+ emission. This work studies the energy coupling of the Er3+ intra-4f transitions and vibrational modes. The results demonstrate that the coupling introduces enormous nonradiative internal relaxation, which condenses the excited erbium population on to the 4I13/2 state. This suggests that vibrational modes can be advantageous for optimizing the branching ratio for the 1.5 μm transition in organic erbium materials. Through control of the quenching effect on to the 4I13/2 state and a reliable determination of intrinsic radiative rates, it is found that the pump power for population inversion can be reduced by an order of magnitude at high erbium concentrations compared to conventional inorganic erbium materials. </p