ABSTRACT
Incoherent digital holography (IDH) with a sequential phase-shifting method enables high-definition 3D imaging under incoherent lights. However, sequential recording of multiple holograms renders IDH impractical for 3D videography. In this study, we propose grating-based in-line geometric-phase-shifting IDH. Our method divides orthogonal circularly polarized lights into four copies with a fabricated phase grating and subsequently creates self-interference holograms with geometric phases introduced by a segmented linear polarizer. This enables single-shot recording of holograms without the need for a specially designed image sensor, such as a polarization-sensitive sensor. Moreover, the achievable spatial resolution is higher than that of off-axis methods. As a proof-of-principle experiment, we demonstrated snapshot and video recording of 3D reflective objects using our IDH method. The results confirmed the feasibility of the proposed method.
ABSTRACT
Incoherent digital holography (IDH) enables the recording of holograms with incoherent light. However, there is unnatural bokeh with ringing on reconstructed 2D images, owing to the diffraction calculation based on the coherent nature of the light. Thus, we propose a transformation method that converts it into incoherent bokeh. This proposed method can generate 2D images without ringing from recorded holograms through a virtual incoherent imaging system, while focusing on the non-linearity problem of reconstruction distances in IDH. Flexible depth-of-field control is also made possible by the judicious selection of parameters in this method. A proof-of-principle demonstration verifies its feasibility.
Subject(s)
Holography , Holography/methodsABSTRACT
Fresnel incoherent correlation holography (FINCH) was a milestone in incoherent holography. In this roadmap, two pathways, namely the development of FINCH and applications of FINCH explored by many prominent research groups, are discussed. The current state-of-the-art FINCH technology, challenges, and future perspectives of FINCH technology as recognized by a diverse group of researchers contributing to different facets of research in FINCH have been presented.
ABSTRACT
Incoherent digital holography (IDH) enables passive 3D imaging through the self-interference of incoherent light. IDH imaging properties are dictated by the numerical aperture and optical layout in a complex manner [Opt. Express27, 33634 (2019)OPEXFF1094-408710.1364/OE.27.033634]. We develop an IDH simulation model to provide insight into its basic operation and imaging properties. The simulation is based on the scalar diffraction theory. Incoherent irradiance and self-interference holograms are numerically represented by the intensity-based summation of each propagation through finite aperture optics from independent point sources. By comparing numerical and experimental results, the applicability, accuracy, and limitation of the simulation are discussed. The developed simulation would be useful in optimizing the IDH setup.
ABSTRACT
Incoherent digital holography (IDH) requires no spatial coherence; however, it requires high temporal coherence for a light source to capture holograms with high spatial resolution. Temporal coherence is often enhanced with a bandpass filter, reducing the light utilization efficiency. Thus, there is a trade-off between spatial resolution and light utilization efficiency. In this paper, we derive a relationship between spatial resolution and temporal coherence by including a conceptual aperture, determined by temporal coherence, in our previous theory of spatial resolution for arbitrary depth planes [Opt. Express27, 33634 (2019)OPEXFF1094-408710.1364/OE.27.033634]. Experimental evaluations verified the effectiveness of our theory, which is useful for the optimization of IDH setups and avoiding the trade-off.
ABSTRACT
An unconventional angular-multiplexed recording technique is proposed for holographic data storage based on a computer-generated hologram (CGH) technique. While general angular-multiplexed recording techniques require a Mach-Zehnder interferometer to record data pages as volume holograms, the proposed method records ones with a common-path configuration with the help of a CGH technique, which prevents the optical setup from being bulky. In the proposed method, the CGH reconstructs signal and reference beams simultaneously, and these beams interfere in a recording medium. By changing the diffraction angle of the reference beam from the CGH, angular multiplexing is accomplished with a common-path optical setup without additional optical elements. Multiplexed recording of four data pages is demonstrated in a proof-of-principle experiment, which indicates the feasibility of the proposed method.
ABSTRACT
Incoherent digital holography (IDH) enables passive 3D imaging under spatially incoherent light; however, the reconstructed images are seriously affected by detector noise. Herein, we derive theoretical sampling requirements for IDH to reduce this noise via simple postprocessing based on spatial averaging. The derived theory provides a significant insight that the sampling requirements vary depending on the recording geometry. By judiciously choosing the number of pixels used for spatial averaging based on the proposed theory, noise can be reduced without losing spatial resolution. We then experimentally verify the derived theory and show that the associated adaptive spatial averaging technique is a practical and powerful way of improving 3D image quality.
ABSTRACT
Although three-dimensional (3D) imaging and extended depth-of-field (DOF) imaging are completely opposite techniques, both provide much more information about 3D scenes and objects than does traditional two-dimensional imaging. Therefore, these imaging techniques strongly influence a wide variety of applications, such as broadcasting, entertainment, metrology, security and biology. In the present work, we derive a generalised theory involving incoherent digital holography to describe both 3D imaging and quasi-infinite-DOF (QIDOF) imaging, which allows us to comprehensively discuss the functions of each imaging technique. On the basis of this theory, we propose and develop a bimodal incoherent digital holography system that allows both 3D imaging and QIDOF imaging. The proposed system allows imaging objects using spatially incoherent light and reconstructing 3D images or QIDOF images solely by changing the phase pattern of a spatial light modulator and without requiring mechanical adjustments or any other modifications to the setup. As a proof-of-principle experiment, we evaluate the DOF and record holograms of a reflective object with the proposed system. The experimental results show that the generalised theory is effective; our demonstration platform provides the function of 3D and QIDOF imaging.
ABSTRACT
To increase the recording density of computer-generated-hologram (CGH)-based holographic data storage, a phase data page reconstruction method by the transport of intensity equation (TIE) is proposed. The TIE generally requires a scanning image sensor because the phase retrieval process needs at least two defocused intensity distributions. Although the TIE is applied, the proposed method enables detection of the distributions simultaneously by utilizing an extra conjugate component reconstructed from the CGH. Experimental results show that the proposed method allows reconstructing of a phase data page without any additional elements, which keeps the optical setup simple and low cost.
ABSTRACT
Single-shot phase-shifting incoherent digital holography with multiplexed checkerboard phase gratings is proposed for acquiring holograms of moving objects. The gratings presented here play the following three roles: dividing the beams, modulating the curvature of spherical beams, and introducing different phase shifts. With the gratings of our proposed method, four individual holograms of a spatially incoherent light are formed on an image sensor. Therefore, it is possible to simultaneously capture four holograms and implement a phase-shifting technique. A proof-of-principle experiment was conducted to show the feasibility of the proposed method.
ABSTRACT
Interpixel cross talk decreases the quality of a reconstructed signal in holographic data storage and imposes a limitation on its storage capacity. To reduce the interpixel cross talk, an orthogonal polarization encoding method is proposed. In the proposed method, the polarization state of each pixel is set to be orthogonal with that of surrounding pixels. This prevents the interference between nearest-neighboring pixels and significantly reduces the gross of the interpixel cross talk. The quality of the data page obtained with the proposed method is numerically and experimentally evaluated. Those results suggest that the proposed method can improve the quality of a reconstructed signal.
ABSTRACT
A holographic data storage system based on a computer-generated hologram (CGH) is simple and compact because a hologram of a data page is recorded through an imaging system without an additional optical path for a reference beam. In this paper, to improve the recording density of the holographic data storage based on a CGH, a shift multiplexing method using a spherical wave is proposed. A data page to be stored and a spherical wave are simultaneously reconstructed from a single CGH. This allows shift multiplexing by displacing a recording medium. Experimental results show that the proposed method can improve shift selectivity and enables us to implement shift multiplexing.
ABSTRACT
Digital super-resolution holographic data storage based on Hermitian symmetry is proposed to store digital data in a tiny area of a medium. In general, reducing a recording area with an aperture leads to the improvement in the storage capacity of holographic data storage. Conventional holographic data storage systems however have a limitation in reducing a recording area. This limitation is called a Nyquist size. Unlike the conventional systems, our proposed system can overcome the limitation with the help of a digital holographic technique and digital signal processing. Experimental result shows that the proposed system can record and retrieve a hologram in a smaller area than the Nyquist size on the basis of Hermitian symmetry.
ABSTRACT
The authors wish to make a change to the published paper [1].[...].
ABSTRACT
Holographic recording media can store the amplitude and the phase, or the complex amplitude, of a beam on the basis of holography. Owing to this characteristic, digital data can be encoded onto the complex amplitude of a signal beam in holographic data storage. However, most of conventional holographic storage systems encode digital data onto the amplitude alone because there are difficulties for modulating and detecting the phase. To solve the difficulties, a holographic storage system using digital holographic techniques has been proposed. With the help of digital holographic techniques, it is possible to modulate and detect the complex amplitude of a signal beam. Moreover, the proposed system can modulate the complex amplitude of a reference beam. In this paper, by making use of the capability, a correlation-based multiplexing with uncorrelated reference beams is demonstrated in the proposed system. Multiple holograms can be recorded in the same volume of a recording medium with no need for mechanical movements. Experimental results show that the proposed system with a correlation-based multiplexing can improve the storage capacity and can utilize the full potential of a recording medium without crosstalk noise stem from the optical setup.
ABSTRACT
A coaxial polarization holographic data recording is proposed, and a proof-of-principle experiment is demonstrated for the first time, to the best of our knowledge. A proposed recording system allows us to record and retrieve a volume polarization hologram using a simple optical setup, as compared with conventional polarization holographic data storage systems. By using the proposed system, the data pages encoded on horizontal and vertical linearly polarized beams were simultaneously recorded, and each data page was successfully retrieved without any error. Moreover, the effectiveness of a random phase mask was experimentally and quantitatively confirmed in polarization holographic data storage.
ABSTRACT
A holographic data storage system using digital holography is proposed to record and retrieve multilevel complex amplitude data pages. Digital holographic techniques are capable of modulating and detecting complex amplitude distribution using current electronic devices. These techniques allow the development of a simple, compact, and stable holographic storage system that mainly consists of a single phase-only spatial light modulator and an image sensor. As a proof-of-principle experiment, complex amplitude data pages with binary amplitude and four-level phase are recorded and retrieved. Experimental results show the feasibility of the proposed holographic data storage system.
ABSTRACT
A linear phase encoding is presented for realizing a compact and simple holographic data storage system with a single spatial light modulator (SLM). This encoding method makes it possible to modulate a complex amplitude distribution with a single phase-only SLM in a holographic storage system. In addition, an undesired light due to the imperfection of an SLM can be removed by spatial frequency filtering with a Nyquist aperture. The linear phase encoding is introduced to coaxial holographic data storage. The generation of a signal beam using linear phase encoding is experimentally verified in an interferometer. In a coaxial holographic data storage system, single data recording, shift selectivity, and shift multiplexed recording are experimentally demonstrated.
ABSTRACT
A multilayer recording method using a varifocal lens generated with a kinoform is presented. In this recording method, a focus position is axially displaced by adding a defocus phase to a phase modulation pattern, which consists of a random phase mask and a computer-generated reference pattern. Shift selectivity and multiplexed recording are experimentally investigated in coaxial holographic data storage. Experimental results show that the proposed method allows the recording of holograms along an optical axis without any mechanical movement.
ABSTRACT
A computer-generated reference pattern (CGRP) allows improvement in light efficiency and the quality of reconstructed data in coaxial holographic data storage. In this Letter, a multiplexed recording method with uncorrelated CGRPs is proposed. With this method, crosstalk from adjacent holograms is suppressed without shifting a medium. To confirm the feasibility of the proposed method experimentally, shift selectivity is investigated, and then multiplexed recording is performed. Experimental results show that the proposed method enables high-density recording compared with conventional shift multiplexing. In addition, a theoretical analysis implies that at least 100 uncorrelated CGRPs can be designed and used for multiplexed recording.
