Digital micromirror devices (DMDs), owing to their rapid refresh rates, are among the most commonly used spatial light modulators in holographic three-dimensional near-eye displays. However, the modulation of DMD is typically confined to binary amplitude modulation, resulting in a noticeable presence of zero-order and conjugate noise, which significantly occupies the spatial bandwidth of the display optics and reduces the quality of optical reconstruction. To address these issues, we propose a computational framework of generating optimized binary computer-generated holograms for DMD-based holographic near-eye displays. Our work employs an iterative-based optimization strategy within a band-limited diffraction computation, thereby enhancing the display quality while achieving a considerable field of view by eliminating zero-order and conjugate noise. The proposed method is verified experimentally by displaying true three-dimensional images with low speckle noise and high contrast, opening a path towards next-generation of virtual reality/augmented reality display devices.
KEYWORDS: Computer generated holography, Holograms, Diffraction, Holography, 3D modeling, Wavefronts, 3D image reconstruction, 3D displays, Holographic displays, 3D acquisition
Holographic display stands as a prominent approach for achieving lifelike three-dimensional (3D) reproductions with continuous depth sensation. However, the generation of a computer-generated hologram (CGH) always relies on the repetitive computation of diffraction propagation from point-cloud or multiple depth-sliced planar images, which inevitably leads to an increase in computational complexity, making real-time CGH generation impractical. Here, we report a new CGH generation algorithm capable of rapidly synthesizing a 3D hologram in only one-step backward propagation calculation in a novel split Lohmann lens-based diffraction model. By introducing an extra predesigned virtual digital phase modulation of multifocal split Lohmann lens in such a diffraction model, the generated CGH appears to reconstruct 3D scenes with accurate accommodation abilities across the display contents. Compared with the conventional layer-based method, the computation speed of the proposed method is independent of the quantized layer numbers, and therefore can achieve real-time computation speed with a very dense of depth sampling. Both simulation and experimental results validate the proposed method.
Diffraction gratings are key components in many applications including pulse compression and stretch, optical imaging, spectral encoding and decoding and optical filtering. In this paper, spatial dispersion of two typical diffraction grating-based optical systems, single-grating system and grating-pair system, are thoroughly studied. The single-grating system consists of a diffraction grating to disperse the quasi-monochromatic lights and a convex lens to make the lights propagate in parallel and focused. In the grating–pair system, a pair of diffraction gratings is used to disperse the collimated lights in parallel. The spatial dispersion law for the two systems is developed and summarized. By investigating the spatial dispersion, the two systems are compared and discussed in detail.
This paper briefly introduces biological sensing based on guided-mode resonance (GMR) effect and two main application models commonly used in biomolecular sensing. The two models are GMR label-free detecting biosensor and GMR enhanced fluorescence bioimager. Using these biosensor and bioimager, the detecting limitation and imaging resolution in current researches are reviewed. We also indicate the detection results and a few achievements in our work. Some other potential applications are also described in the paper.
One method of adjusting the characteristic deviations of Guided mode resonant filters (GMRFs) induced by preparing errors is derived by using the cover layer of GMRFs. The investigations of GMRFs are reported widely for their merits such as high efficiency, narrow bandwidth and low sideband. But there are few reports about the preparation and commercial application of GMRFs. The reason for this is that the characteristics of GMRFs are strict with the error of preparation. The data of this paper shows the linear relationship between the grating depth and the resonant wavelength in the grating depth error range of 0-12 nm. It is shown that the cover layer of GMRFs has adjusting effect on the characteristics of GMRFs. Through choosing material and adjusting the thickness of cover layer, these deviations induced by preparing errors cay be adjusted perfectly.
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