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Holography|40 Article(s)
Real-time spatiotemporal division multiplexing electroholography for 1,200,000 object points using multiple-graphics processing unit cluster
Hiromi Sannomiya, Naoki Takada, Kohei Suzuki, Tomoya Sakaguchi, Hirotaka Nakayama, Minoru Oikawa, Yuichiro Mori, Takashi Kakue, Tomoyoshi Shimobaba, and Tomoyoshi Ito
Computationally, the calculation of computer-generated holograms is extremely expensive, and the image quality deteriorates when reconstructing three-dimensional (3D) holographic video from a point-cloud model comprising a huge number of object points. To solve these problems, we implement herein a spatiotemporal division multiplexing method on a cluster system with 13 GPUs connected by a gigabit Ethernet network. A performance evaluation indicates that the proposed method can realize a real-time holographic video of a 3D object comprising ～1,200,000 object points. These results demonstrate a clear 3D holographic video at 32.7 frames per second reconstructed from a 3D object comprising 1,064,462 object points. Computationally, the calculation of computer-generated holograms is extremely expensive, and the image quality deteriorates when reconstructing three-dimensional (3D) holographic video from a point-cloud model comprising a huge number of object points. To solve these problems, we implement herein a spatiotemporal division multiplexing method on a cluster system with 13 GPUs connected by a gigabit Ethernet network. A performance evaluation indicates that the proposed method can realize a real-time holographic video of a 3D object comprising ～1,200,000 object points. These results demonstrate a clear 3D holographic video at 32.7 frames per second reconstructed from a 3D object comprising 1,064,462 object points.
Chinese Optics Letters
- Publication Date: Jul. 10, 2020
- Vol. 18, Issue 7, 070901 (2020)
Use of focus stacking and SfM techniques in the process of registration of a small object hologram
Sławomir Paśko, Marek Sutkowski, and Ramunas Bakanas
In this Letter, a method for shape visualization of small objects (microscopic) in the form of a hologram is presented. It consists of a standard optical set-up for small object registration (i.e., stereoscopic or biological microscope). The focus stacking technique is used to obtain a series of images with increased depth of field and on them a shape reconstruction procedure (structure from motion, SfM) is made. With use of a dense cloud of points, a sequence of parallax-related images suitable for Geola’s digital holographic printing is generated. The holographic printer produces single-parallax holographic (full three-dimensional) images of real or virtual objects. In this Letter, a method for shape visualization of small objects (microscopic) in the form of a hologram is presented. It consists of a standard optical set-up for small object registration (i.e., stereoscopic or biological microscope). The focus stacking technique is used to obtain a series of images with increased depth of field and on them a shape reconstruction procedure (structure from motion, SfM) is made. With use of a dense cloud of points, a sequence of parallax-related images suitable for Geola’s digital holographic printing is generated. The holographic printer produces single-parallax holographic (full three-dimensional) images of real or virtual objects.
Chinese Optics Letters
- Publication Date: Jun. 10, 2020
- Vol. 18, Issue 6, 060901 (2020)
Real-time electroholography using a single spatial light modulator and a cluster of graphics-processing units connected by a gigabit Ethernet network
Hiromi Sannomiya, Naoki Takada, Tomoya Sakaguchi, Hirotaka Nakayama, Minoru Oikawa, Yuichiro Mori, Takashi Kakue, Tomoyoshi Shimobaba, and Tomoyoshi Ito
Systems containing multiple graphics-processing-unit (GPU) clusters are difficult to use for real-time electroholography when using only a single spatial light modulator because the transfer of the computer-generated hologram data between the GPUs is bottlenecked. To overcome this bottleneck, we propose a rapid GPU packing scheme that significantly reduces the volume of the required data transfer. The proposed method uses a multi-GPU cluster system connected with a cost-effective gigabit Ethernet network. In tests, we achieved real-time electroholography of a three-dimensional (3D) video presenting a point-cloud 3D object made up of approximately 200,000 points. Systems containing multiple graphics-processing-unit (GPU) clusters are difficult to use for real-time electroholography when using only a single spatial light modulator because the transfer of the computer-generated hologram data between the GPUs is bottlenecked. To overcome this bottleneck, we propose a rapid GPU packing scheme that significantly reduces the volume of the required data transfer. The proposed method uses a multi-GPU cluster system connected with a cost-effective gigabit Ethernet network. In tests, we achieved real-time electroholography of a three-dimensional (3D) video presenting a point-cloud 3D object made up of approximately 200,000 points.
Chinese Optics Letters
- Publication Date: Feb. 10, 2020
- Vol. 18, Issue 2, 020902 (2020)
Multi-reference lens-less Fourier-transform holography with a Greek-ladder sieve array
Jing Xie, Junyong Zhang, Xue Pan, Shenlei Zhou, and Weixin Ma
Lens-less Fourier-transform holography has been actively studied because of its simple optical structure and its single-shot recording. However, a low-contrast interferogram between the reference and object waves limits its signal to noise ratio. Here, multi-reference lens-less Fourier-transform holography with a Greek-ladder sieve array is proposed in the experiment and demonstrated effectively to improve the signal to noise ratio. The key technique in our proposed method is a Greek-ladder sieve array, which acts as not only a wave-front modulator but also a beam splitter. With advantages of the common path, single shot, and no need for a lens, this system has enormous potential in imaging and especially in extreme ultraviolet and soft X-ray holography. Lens-less Fourier-transform holography has been actively studied because of its simple optical structure and its single-shot recording. However, a low-contrast interferogram between the reference and object waves limits its signal to noise ratio. Here, multi-reference lens-less Fourier-transform holography with a Greek-ladder sieve array is proposed in the experiment and demonstrated effectively to improve the signal to noise ratio. The key technique in our proposed method is a Greek-ladder sieve array, which acts as not only a wave-front modulator but also a beam splitter. With advantages of the common path, single shot, and no need for a lens, this system has enormous potential in imaging and especially in extreme ultraviolet and soft X-ray holography.
Chinese Optics Letters
- Publication Date: Feb. 10, 2020
- Vol. 18, Issue 2, 020901 (2020)
Spatiotemporal double-phase hologram for complex-amplitude holographic displays
Xiaomeng Sui, Zehao He, Hao Zhang, Liangcai Cao, Daping Chu, and Guofan Jin
This Letter describes an approach to encode complex-amplitude light waves with spatiotemporal double-phase holograms (DPHs) for overcoming the limit of the space-bandwidth product (SBP) delivered by existing methods. To construct DPHs, two spatially macro-pixel encoded phase components are employed in the SBP-preserved resampling of complex holograms. Four generated sub-DPHs are displayed sequentially in time for high-quality holographic image reconstruction without reducing the image size or discarding any image terms when the DPHs are interweaved. The reconstructed holographic images contain more details and less speckle noise, with their signal-to-noise ratio and structure similarity index being improved by 14.64% and 78.79%, respectively. This Letter describes an approach to encode complex-amplitude light waves with spatiotemporal double-phase holograms (DPHs) for overcoming the limit of the space-bandwidth product (SBP) delivered by existing methods. To construct DPHs, two spatially macro-pixel encoded phase components are employed in the SBP-preserved resampling of complex holograms. Four generated sub-DPHs are displayed sequentially in time for high-quality holographic image reconstruction without reducing the image size or discarding any image terms when the DPHs are interweaved. The reconstructed holographic images contain more details and less speckle noise, with their signal-to-noise ratio and structure similarity index being improved by 14.64% and 78.79%, respectively.
Chinese Optics Letters
- Publication Date: Oct. 10, 2020
- Vol. 18, Issue 10, 100901 (2020)
Real-time color holographic video reconstruction using multiple-graphics processing unit cluster acceleration and three spatial light modulators
Shohei Ikawa, Naoki Takada, Hiromitsu Araki, Hiroaki Niwase, Hiromi Sannomiya, Hirotaka Nakayama, Minoru Oikawa, Yuichiro Mori, Takashi Kakue, Tomoyoshi Shimobaba, and Tomoyoshi Ito
We demonstrate real-time three-dimensional (3D) color video using a color electroholographic system with a cluster of multiple-graphics processing units (multi-GPU) and three spatial light modulators (SLMs) corresponding respectively to red, green, and blue (RGB)-colored reconstructing lights. The multi-GPU cluster has a computer-generated hologram (CGH) display node containing a GPU, for displaying calculated CGHs on SLMs, and four CGH calculation nodes using 12 GPUs. The GPUs in the CGH calculation node generate CGHs corresponding to RGB reconstructing lights in a 3D color video using pipeline processing. Real-time color electroholography was realized for a 3D color object comprising approximately 21,000 points per color. We demonstrate real-time three-dimensional (3D) color video using a color electroholographic system with a cluster of multiple-graphics processing units (multi-GPU) and three spatial light modulators (SLMs) corresponding respectively to red, green, and blue (RGB)-colored reconstructing lights. The multi-GPU cluster has a computer-generated hologram (CGH) display node containing a GPU, for displaying calculated CGHs on SLMs, and four CGH calculation nodes using 12 GPUs. The GPUs in the CGH calculation node generate CGHs corresponding to RGB reconstructing lights in a 3D color video using pipeline processing. Real-time color electroholography was realized for a 3D color object comprising approximately 21,000 points per color.
Chinese Optics Letters
- Publication Date: Jan. 10, 2020
- Vol. 18, Issue 1, 010901 (2020)
Ultra-lightweight and wide field of view augmented reality virtual retina display based on optical fiber projector and volume holographic lens
Zhidong Chen, Xinzhu Sang, Hui Li, Yuan Wang, and Linmin Zhao
A novel see-through virtual retina display (VRD) system is proposed in this Letter. An optical fiber projector is used as the thin-light-beam source, which is modified from a laser scan projector by separating the laser sources and the scan mechanical structure. A synthetic aperture method is proposed for simple, low-cost fabrication of a volume holographic lens with large numerical aperture. These two key performance-enhanced elements are integrated into a lightweight and ordinary-glasses-like optical see-through VRD system. The proposed VRD system achieves a weight of 30 g and a diagonal field of view of 60°. A novel see-through virtual retina display (VRD) system is proposed in this Letter. An optical fiber projector is used as the thin-light-beam source, which is modified from a laser scan projector by separating the laser sources and the scan mechanical structure. A synthetic aperture method is proposed for simple, low-cost fabrication of a volume holographic lens with large numerical aperture. These two key performance-enhanced elements are integrated into a lightweight and ordinary-glasses-like optical see-through VRD system. The proposed VRD system achieves a weight of 30 g and a diagonal field of view of 60°.
Chinese Optics Letters
- Publication Date: Sep. 10, 2019
- Vol. 17, Issue 9, 090901 (2019)
Optimization of compensation for high spatial frequency in distorted wavefront using optical phase conjugation
Pan Zhang, Dean Liu, Aihua Yang, and Jianqiang Zhu
A method is proposed to optimize the recording structure of the photorefractive volume grating to compensate high spatial frequency in the distorted wavefront by optical phase conjugation. Based on the coupled-wave equation, the diffraction efficiency of the recorded grating formed by the scattered beams in different recording structures is simulated. The theoretical results show that the recorded modulations with high spatial frequency can be significantly improved in the small recording angle. In the experiment, three recording structures with the recording angles of 7.5°, 30°, and 45° are chosen to verify the compensation effect. Compared with the reconstructed image in the large recording angle of 45°, the signal to noise ratio of the image recorded at 7.5° increases to 3.2 times of that at 45°. A method is proposed to optimize the recording structure of the photorefractive volume grating to compensate high spatial frequency in the distorted wavefront by optical phase conjugation. Based on the coupled-wave equation, the diffraction efficiency of the recorded grating formed by the scattered beams in different recording structures is simulated. The theoretical results show that the recorded modulations with high spatial frequency can be significantly improved in the small recording angle. In the experiment, three recording structures with the recording angles of 7.5°, 30°, and 45° are chosen to verify the compensation effect. Compared with the reconstructed image in the large recording angle of 45°, the signal to noise ratio of the image recorded at 7.5° increases to 3.2 times of that at 45°.
Chinese Optics Letters
- Publication Date: Jul. 10, 2019
- Vol. 17, Issue 7, 070901 (2019)
Three-dimensional position measurement of a levitated nanoparticle in a vacuum by a Dove prism
Yu Zheng, and Fangwen Sun
Forward-scattering-light interferometry has become the most commonly used position detection scheme in optical levitation systems. Usually, three-set detectors are required to obtain the three-dimensional motion information. Here, we simplify the three-set detectors to one set by inserting a Dove prism. We investigate the role of a Dove prism in the position measurement process with an optical levitation system in vacuum. The relationship between the power spectral density and the rotation angle of a Dove prism is experimentally demonstrated and analyzed. This work shows that the Dove prism can greatly reduce the complexity of the experimental setup, which can be applied to compact optical levitation systems for studies in metrology, quantum physics, and biology. Forward-scattering-light interferometry has become the most commonly used position detection scheme in optical levitation systems. Usually, three-set detectors are required to obtain the three-dimensional motion information. Here, we simplify the three-set detectors to one set by inserting a Dove prism. We investigate the role of a Dove prism in the position measurement process with an optical levitation system in vacuum. The relationship between the power spectral density and the rotation angle of a Dove prism is experimentally demonstrated and analyzed. This work shows that the Dove prism can greatly reduce the complexity of the experimental setup, which can be applied to compact optical levitation systems for studies in metrology, quantum physics, and biology.
Chinese Optics Letters
- Publication Date: Jun. 10, 2019
- Vol. 17, Issue 6, 060901 (2019)
Integrating multiple images in a sampled phase-only hologram
P. W. M. Tsang, T.-C. Poon, W. Wang, X. Zhu, and K. Chan
Past research has demonstrated that a sampled phase-only hologram (SPOH) is capable of representing an image without the magnitude component of the hologram. At present, an SPOH can only record and reconstruct a single source image. In this Letter, we propose, for the first time, to the best of our knowledge, a method for representing multiple images with a single integrated SPOH (ISPOH). Subsequently, each image can be retrieved from the ISPOH with a unique key parameter and displayed as a visible image on a phase-only spatial light modulator. Past research has demonstrated that a sampled phase-only hologram (SPOH) is capable of representing an image without the magnitude component of the hologram. At present, an SPOH can only record and reconstruct a single source image. In this Letter, we propose, for the first time, to the best of our knowledge, a method for representing multiple images with a single integrated SPOH (ISPOH). Subsequently, each image can be retrieved from the ISPOH with a unique key parameter and displayed as a visible image on a phase-only spatial light modulator.
Chinese Optics Letters
- Publication Date: May. 10, 2019
- Vol. 17, Issue 5, 050901 (2019)
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