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Imaging the Living Eye
Published in Margarida M. Barroso, Xavier Intes, In Vivo, 2020
Brian T. Soetikno, Lisa Beckmann, Hao F. Zhang
Once the aberrations are sensed, predistortions can be introduced to the illumination light using a deformable mirror. The deformable mirror is a 2D mirror array in which each mirror can be individually translated to adjust the optical pathlength for a portion of the illumination beam reflected by the particular mirror. Collectively, the 2D mirror away can predistort the illumination beam into the opposite wavefront comparing with the detected aberrations by the SHWS. Such correction process is usually iterative, and near diffraction-limited resolution can be achieved in retinal imaging.
Optical MEMS for space
Published in Guangya Zhou, Chengkuo Lee, Optical MEMS, Nanophotonics, and Their Applications, 2017
Wavefront correction like adaptive optics systems is based on a combination of three elements, namely the wavefront sensor for the measurement of the shape of the wavefront arriving in the telescope, the deformable mirror as the wavefront correcting element, and, finally, the real time computer closing the loop of the system at a frequency ranging from 0.5 to 2 kHz in order to follow the evolution of the atmospheric fluctuations (Figure 4.3).
D
Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
deferred evaluation deferred evaluation a scheduling policy under which a task is not scheduled until it has been determined that the results of that task are required by another task that is in execution and cannot proceed without these results. definite time DC motor acceleration when DC motors accelerate during their starting sequence, starting resistors are removed from the armature circuit in steps. In definite time DC motor acceleration (also referred to as open loop DC motor acceleration), the starting resistors are removed in definite time increments, whether the motor is actually accelerating or not. definite-purpose motor any motor design, listed and offered in standard ratings with standard operating characteristics, with special mechanical features for use under service conditions other than usual or for use on a particular type of application. definition phase or statement in which a new type, or a class, or a frame for variables is defined. The definition of typed constant is also typically allowed. deflector any of a number of optical devices that change the direction of an optical beam, using mechanisms such as diffraction, mechanical mirror motion, and refraction. defocus the distance, measured along the optical axis (i.e., perpendicular to the plane of the best focus) between the position of a resist-coated wafer and the position if the wafer were at best focus. defocusing quadrupole magnet a quadrupole magnet that focuses beam in the vertical plane and defocuses in the horizontal plane. DeForest, Lee Bluffs, Iowa. (1873-1961) Born: Council Best known for his contributions to the development of radio communications. DeForest's greatest invention was called the audion triode. This vacuum tube was based on an earlier patented tube developed by John A. Fleming. This tube, which was both an amplifier and a rectifier, allowed the development of radios, radar, television, and some early computers. DeForest's life was noted for controversial, and often poor, business decisions. deformable mirror device a type of device for light modulation, especially spatial light modulation, employing micromechanical structures, such as cantilevered mirrors or mirrors with torsional motions, to deflect incident light rays. defuzzification the process of transforming a fuzzy set into a crisp set or a real-valued number. defuzzifier a fuzzy system that produces a crisp (non fuzzy) output from the results of the fuzzy inference engine. The most used defuzzifiers are (1) maximum defuzzifier that selects as its output the value of y for which the membership of the output membership function µ B (y) is maximum; (2) centroid defuzzifier determines the center of gravity (centroid), y of B, and uses this value as the output of the fuzzy inference system. See also fuzzy inference engine, fuzzy inference system. degenerate common emitter a combination of the common-emitter and emitter-follower stages with a very well-defined gain. degenerate four-wave mixing a four-wave mixing process in which all of the interacting waves have the same frequency. In certain geometrical arrangements, this process leads to optical phase conjugation and in addition can be for certain types of optical information processing. degenerate modes two modes with different field structures having the same cutoff frequency
Development of adaptive optical correction and polarization control modules for 10-km free-space coherent optical communications
Published in Journal of Modern Optics, 2020
This module uses stochastic parallel gradient descent (SPGD) algorithm to correct the wavefront distortions with the optical power value coupled into single-mode optical fibre as the objective function. The real-time correction of wave aberration can be realized by driving the deformable mirror (DM) to generate a suitable surface shape according to the value of the objective function.