Session Index

The holographic optical engine that is composed of a spatial light modulator (SLM), image sensors, relay optics, and a control computer performs an optimization of a computer-generated hologram (CGH) in an optical system. The CGH optimized before or during laser processing generates two- and three-dimensional focusing spots with an automatic compensation of static imperfections and dynamic changes in the optical system, therefore the holographic laser processing is performed with high stability, high-throughput, and high usability.

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We proposed several methods to improve the image quality in a diffractive additive manufacturing (DAM) system in which a sequence of diffractive optical elements (DOEs) encoding slice images of 3D objects produce volumetric images for polymerizing photosensitive resins. Adding a linear phase to the DOE function to shift the diffraction images away from the reflection of the SLM window, stacking multiple diffraction images of random phases to smoothen the speckle effect, and varying the intensity of diffraction image to increase the longitudinal continuousness, we successfully achieved a DAM system with high efficiency, high resolution, fast working speed and good continuity.

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In recent years, digital holographic microscopy has been well-developed. It gets the advantages of high-speed phase imaging, quantitative phase imaging, and digital focusing without losing image quality. However, current commercial holographic microscopes are too bulky and expensive. Therefore, this paper proposed a volume holographic optical waveguide element combined with a digital holographic microscope to form a volume holographic lens-less digital holographic microscope. In the experiment, we successfully minimized the Lens-less Fourier Transform Digital Holographic Microscope, which has the advantages of high NA, minimizable body, and optical zoom. Furthermore, it can switch magnification without changing the object distance.

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In this study, we use MATLAB to model a plano-convex spherical lens for the microwave band which was fabricated with photopolymerization additive manufacturing technology. The results show that when the resolution of the printer meets the conditions, we can simulate the lens model by determining the lens focal length and curvature radius with MATLAB, and import the simulated model into the additive manufacturing software for editing. Finally, a lens with a radius of 50mm was successfully printed, and the flatness of the lens at wavelength of 2.85cm can also reach the high standard of λ/50.

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A developed deep learning based computer-generated holography (DeepCGH) can real-time stimulate neurons; however, the computation time as growing the number of input layers is increased and arbitrary 3D micropatterned cannot be reconstructed. Herein, a digital propagation matrix (DPM) containing the depth information of customized micropatterns is intergraded into DeepCGH to generate arbitrary 3D micropatterns and shorten the computation time. As a result, the DeepCGH with DPM could timely generate the customized micropatterns within a 300-μm volume with high accuracy. Furthermore, the DeepCGH hologram is rapidly displayed on spatial light modulator.

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In this study, a misalignment measurement method was proposed which based on grating-type heterodyne interferometry. The dislocation between two parallel gratings can be obtained and the optimum dislocation between them can be within 0.1% under the displacement of 100 µm.

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In this paper, the respective coherence properties of laser and sLED are measured
and the extent discussions are made to study how they affect the speckle noise in the
reconstructed images from a computer generated hologram. It can be seen from the results that
temporal coherence and speckle are positively correlated, but not proportional. This work
paves the way to compact and dynamical holographic displays free of speckle noise.

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