Development And Preliminary Application Of The Seven-channel Incoherent Beam Wavefront Corrector For Defocus Compensation

In the laser active illumination imaging system,due to the transmission of laser in turbulent atmosphere,the laser has serious problems,such as the illumination echo is insufficient in brightness,the illumination uniformity is insufficient,and the light intensity is severely flickered.The incoherent combining array beam is used in the laser active illumination imaging system,which can effectively improve the illumination effect.In order to further improve the imaging quality and improve the target tracking and recognition accuracy,it is necessary to correct the wavefront of the incoherent array beam.Reference to the wavefront correction of single beam,using adaptive optics(AO)technology to integrally control the wavefront of incoherent array beams is one of the effective solutions to improve the quality and energy density of incoherent array beams.It can effectively improve the illumination effect.The seven-channel incoherent beam wavefront corrector for defocus compensation is an integrated wavefront corrector with scalable-size,which can be applied to the incoherent array beam wavefront control system.Compared with the independent adjustment of the sub-beam wavefront with the conventional wavefront corrector,the advantage is that it can simultaneously perform integrated wavefront control.With this method,it can reduce the complexity of the optical system,reduce the assembly difficulty,and reduce the technical requirements for device support and synchronous control.For the incoherent combining of fiber lasers,the distortion wavefront of each sub-beam is mainly low-order aberrations such as defocus,astigmatism,coma,and spherical aberration,while the defocus component accounts for a large proportion.In this thesis,the seven-channel incoherent beam wavefront corrector for defocus compensation with good correction ability and large stroke is designed and fabricated.The far-field spot diameter and voltage relationship are used as the control algorithm.Constructing five-channel incoherent array beam system about integrating control of the wavefront defocus position,verifies the ability for defocus correction and its effect on the control of the wavefront defocus position.The surface deformability of the seven-channel incoherent beam wavefront corrector for defocus compensation is analyzed based on simulation.The surface deformability of each electrode is relatively balanced,that the PV value of each electrode influence function is about 0.9?m.Then the experimental test is carried out.The mirror surface of each electrode has no coupling.Influenced by some factors such as glue layer and processing technology,the measured deformability is much higher than the simulation value.It is between 1.742?m?2.056?m.Then,the theoretical analysis and experimental study on the relationship between the far-field spot diameter and voltage are carried out.It is found that the far-field spot diameter has a one-to-one correspondence with the voltage.The main factor,that affects its own far-field spot diameter,is the different defocus of each sub-beam.In this case,the first electrode is selected as the research object to compare with the positive and negative defocus correction before and after the aberration fitting.The defocus term is well corrected and the corrected zernike coefficient values respectively reach 0.142 and 0.087.Finally,the experiment was carried out by constructing seven-channel incoherent array beam system about integrating control of the wavefront defocus position.The far-field superimposed spot was measured at the same exposure time.The spot diameter was reduced from 485.88?m to 265.5?m,while the power in the bucket was increased from0.3758 to 0.6925.From the result,we could see that the energy concentration is improved by 0.84 times.The wavefront focus position control effect is obvious,which indicates that the seven-channel incoherent beam wavefront corrector for defocus compensation designed and processed by this subject has good ability about defocus correction.In summary,it is suitable for multi-channel incoherent array beam system about integrating control of the wavefront defocus position.