A new scheme for optimizing a computer-generated hologram (CGH) in holographic laser processing system is proposed. The CGH that generates two- and three-dimensionally arranged focusing spots is optimized during laser processing. The scheme called as an in-system optimization has the potential to compensate for static imperfections and dynamic changes of the laser processing system by the rewritable capability of a liquid crystal on silicon spatial light modulator (LCOS-SLM).
We proposed an optimization method of a hologram in holographic laser processing. The laser beam was diffracted by a
designed computer-generated hologram (CGH) displayed on a liquid-crystal-on-silicon (SLM), and then formed
spatially shaped three-dimensional optical pattern which detected by a CCD image sensor at different focal position for
continuously optimizing with the weighted iterative Fourier transform (WIFT) algorithm. The uniformity of the pattern
was increased from 11% to 95%, which was also well proved by the corresponding 3D processing results. This method
provides the holographic laser processing system with high-stability, that is, the ability to dynamically compensate for
system imperfections, and has the ability to be suitable for a wide range of high-precision, high-throughput applications
in the field of 3D manufacturing.
A method that realizes the three-dimensional holographic laser reconstruction and processing by using an optimized computer-generated hologram (CGH) was demonstrated. A pre-designed CGH that contains three-dimensional (3D) information displayed on a liquid-crystal-on-silicon spatial light modulator (LCOS-SLM) can obtain the desired 3D diffraction pattern in the optical system, called 3D holographic laser reconstruction, and when it is reduced by an objective lens and incident on a sample, it can realize the 3D holographic laser processing. Using an optimization method, called in-system optimization, to compensate for the imperfections that exist in the actual laser system, and obtain the high-quality CGH. Consequently, a high uniformity 3D holographic laser reconstruction was achieved, and the consistent scale of the corresponding processing holes proved the feasibility and significance of the CGH optimization.
We proposed a holographic laser processing system with the combination of femtosecond laser and the in-system optimization. Femtosecond laser processing that employ a computer-generated hologram (CGH) displayed on a liquid-crystal-on-silicon spatial light modulator (LCOS-SLM), called holographic femtosecond laser processing (HFLP). Due to the inherent aberrations of the actual optical system, the diffraction peaks of holographic femtosecond laser processing has non-uniformity. To overcome this problem, we demonstrated a method called in-system optimization that optimizing the uniformity of the diffraction peaks while conducting the laser processing simultaneously. By taking advantage of the rewritable capability of the LCOS-SLM, with finite times of iteration perform of the in-system optimization, we obtained uniform peaks of 0.96, when the maximum intensity at the peaks of the diffraction spots was normalized to 1.0. Make use of this system, we realized the high efficiency and uniformity of laser processing, and made compensation for part of the inherent aberration in the optical system. In particular, we believe it can not only effectively avoid the impact of environmental factors on the processing system and will greatly improve the processing efficiency and stability, in the meanwhile, it will be widely applied for precise laser processing in the future.
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