Abstract
Magnetic fluid is a stable colloidal suspension of nano-sized, single-domain ferri/ferromagnetic particles dispersed in a liquid carrier. The liquid can be magnetized by the ferromagnetic particles aligned with the external magnetic field, which can be used as a wavefront corrector to correct the large aberrations up to more than 100 µm in adaptive optics (AO) systems. Since the measuring range of the wavefront sensor is normally small, the application of the magnetic fluid deformable mirror (MFDM) is limited with the WFS based AO system. In this paper, based on the MFDM model and the relationship between the second moment (SM) of the aberration gradients and the far-field intensity distribution, a model-based wavefront sensorless (WFSless) control algorithm is proposed for the MFDM. The correction performance of MFDM using the model-based control algorithm is evaluated in a WFSless AO system setup with a prototype MFDM, where a laser beam with unknown aberrations is supposed to produce a focused spot on the CCD. Experimental results show that the MFDM can be used to effectively compensate for unknown aberrations in the imaging system with the proposed model-based control algorithm.
Highlights
Magnetic fluid is a stable colloidal suspension of nano-sized, single-domain ferri/ferromagnetic particles dispersed in a liquid carrier
magnetic fluid deformable mirror (MFDM) model and the relationship between the second moment (SM) of the aberration gradients and the far-field intensity distribution, a model-based wavefront sensorless (WFSless) control algorithm is proposed for the MFDM
The correction performance of MFDM using the model-based control algorithm is evaluated in a WFSless adaptive optics (AO) system setup with a prototype MFDM, where a laser beam with unknown aberrations is supposed to produce a focused spot on the CCD
Summary
Magnetic fluid is a stable colloidal suspension of nano-sized (about 10 nm in diameter), single-domain ferri/ferromagnetic particles dispersed in a liquid carrier. In order to extend the applications of MFDM for the large aberration correction, in this paper, a model-based wavefront sensorless control method for toMFDM actuators. WFSless AO systems control approach only uses Z+1 photodetector measurement for the Z aberration modes as the operate by sequentially modulating the WFC and maximizing a feedback signal according to particular predetermined bias functions, theThe correction capability andcontrol the convergence of the AO system optimization algorithms. Typical WFSless model-free methods needspeed many intensity measurements or evaluations of the metric function, which limit the convergence rate of AO systems are improved. The surface dynamic model of the magnetic fluid deformable mirror is first relationship between the performance index and the control input to design the control algorithms, established, such based the [19], mapping relationship between the [20].
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