Incoherent Digital Holography Research Articles

Technology Selection for Inline Topography Measurement with Rover-Borne Laser Spectrometers.

This work studies enhancing the capabilities of compact laser spectroscopes integrated into space-exploration rovers by adding 3D topography measurement techniques. Laser spectroscopy enables the in situ analysis of sample composition, aiding in the understanding of the geological history of extraterrestrial bodies. To complement spectroscopic data, the inclusion of 3D imaging is proposed to provide unprecedented contextual information. The morphological information aids material characterization and hence the constraining of rock and mineral histories. Assigning height information to lateral pixels creates topographies, which offer a more complete spatial dataset than contextual 2D imaging. To aid the integration of 3D measurement into future proposals for rover-based laser spectrometers, the relevant scientific, rover, and sample constraints are outlined. The candidate 3D technologies are discussed, and estimates of performance, weight, and power consumptions guide the down-selection process in three application examples. Technology choice is discussed from different perspectives. Inline microscopic fringe-projection profilometry, incoherent digital holography, and multiwavelength digital holography are found to be promising candidates for further development.

Computational Optical Scanning Holography

Holographic techniques are indispensable tools for modern optical engineering. Over the past two decades, research about incoherent digital holography has continued to attract attention. Optical scanning holography (OSH) can obtain incoherent holograms using single-pixel detection and structured illumination with Fresnel zone patterns (FZPs). Particularly by changing the size of a detector, OSH can also obtain holograms under coherently illuminated conditions. Since 1979, OSH has continuously evolved. According to the evolution of semiconductor technology, spatial light modulators (SLMs) come to be useful for various imaging fields. By using SLM techniques for OSH, the practicality of OSH is improved. These SLM-based OSH methods are termed computational OSH (COSH). In this review, the configurations, recording and reconstruction methods, and proposed applications of COSH are reviewed.

Computational adaptive telescope imaging via self-interference digital holography

Conventional optical telescope only collect the amplitude of optical wavefront with incoherent light, while self-interference incoherent digital holography offers a unique method of coding both the optical wavefront amplitude and phase information by interference patterns. We developed an adaptive non-scanning three-dimensional (3D) telescopic imaging technique based on self-interference incoherent holography with a geometric phase lens (GP-SIDH). The phase recorded in the point spread hologram and the incoherent self-interference extended holograms are employed to detect spatial positions, correct optical aberration and extract edges by computational reconstruction. The 3D imaging and position detection performances of our proposed method are investigated. Both simulations and experimental results show that the proposed method exhibits better performances for different depth objects imaging and space position detection. Furthermore, this system can be easily modularization and implanted into any existing optical telescopic system owing to its simplicity and convenience. The proposed approach can be a powerful tool for the multi-objects long-working-distance imaging, which is more valuable for telescope application.

General phase-difference imaging of incoherent digital holography.

The hologram formed by incoherent holography based on self-interference should preserve the phase difference information of the object, such as the phase difference between the mutually orthogonal polarizations of anisotropic object. How to decode this phase difference from this incoherent hologram, i.e., phase-difference imaging, is of great significance for studying the properties of the measured object. However, there is no general phase-difference imaging theory due to both diverse incoherent holography systems and the complicated reconstruction process from holograms based on the diffraction theory. To realize phase-difference image in incoherent holography, the relationship between the phase difference of the object and the image reconstructed by holograms is derived using a general physical model of incoherent holographic systems, and then the additional phase that will distort this relationship in actual holographic systems is analyzed and eliminated. Finally, the phase-difference imaging that is suitable for the most incoherent holographic systems is realized and the general theory is experimentally verified. This technology can be applied to phase-difference imaging of anisotropic objects, and has potential applications in materials science, biomedicine, polarized optics and other fields.

Single‐shot phase‐shifting on Michelson interferometry for incoherent digital holography

AbstractA single‐shot phase‐shifting method in incoherent digital holography (IDH) based on Michelson interferometry is proposed herein. The proposed method uses polarization‐modulating optical elements and a polarization sensor in the Michelson interferometer optics to induce a geometric phase shift. It acquires four holograms with different geometric phase retardations in a single exposure to eliminate the bias and conjugate noise using a phase‐shifting technique. The proposed optical system enables real‐time bias and conjugate term removal from a recorded hologram without requiring sequential recording for phase shifting. Furthermore, because it is based on Michelson interferometry, it can be implemented using simple reflective optics without expensive or difficult‐to‐produce optical elements for single‐shot phase shifting. The principles of self‐interference and geometric phase shifting in the proposed optical structure were analyzed mathematically. A real‐time IDH‐recording experimental setup was constructed to verify the proposed method. The experimental results of single‐shot phase‐shifting IDH and hologram movie recordings confirm the feasibility of the proposed method.

Aperture Control for Increasing Hologram Signal Amplitude in Incoherent Digital Holography

Aperture Control for Increasing Hologram Signal Amplitude in Incoherent Digital Holography

Incoherent Digital Holography Aiming to Capture Three-Dimensional Video

Incoherent Digital Holography Aiming to Capture Three-Dimensional Video

Incoherent digital holography with two polarization-sensitive phase-only spatial light modulators and reduced number of exposures.

I propose methods for reducing the number of exposures in incoherent digital holography with two polarization-sensitive phase-only spatial light modulators (IDH with TPP-SLMs). In IDH with TPP-SLMs, no polarization filters are required, and not only three-dimensional (3D), but polarization information is also obtained. However, seven exposures are required to conduct filter-free polarimetric incoherent holography. In this article, the optical designs and modified phase-shifting interferometry to reduce the number of recordings are described. IDH with TPP-SLMs has the potential for filter-free single-shot multidimensional incoherent holographic imaging.

On the optical performance of incoherent digital holography for extended 3D objects

Digital Holography (DH) technology has grown fast over the years, offering the possibility to encode complex information from three-dimensional real-world objects onto two-dimensional digital supports. Accessing the object as an entire numerical complex wavefront raised large expectations in the fields of imaging and display. Holographic vision through fog, smoke, and flames in the far infrared (IR) range would be, in principle, applicable to the fields of automotive, video surveillance, and homeland security. However, the need for bulky, high-coherence laser sources has dampened the enthusiasm around the development of holographic cameras for use in such a context. Here, we investigate self-interference digital holography (SIDH) as a method for obtaining refocusable wavefronts by using low-coherence light sources, a category including light bulbs, arc lamps, light-emitting diodes, low-coherence IR lasers, heat sources, and sunlight. We develop and analyze a model to study the optical performance of SIDH in terms of reconstruction distance range, lateral magnification, resolution, and limiting factors. Then, we propose a configuration for reshaping the system Point Spread Function (PSF) and enhancing resolution by tuning the visibility of high-frequency fringes. The model is experimentally verified by imaging various scenes under incoherent illumination in the visible range. As a last testbed, we provide a first proof of concept SIDH imaging in the far IR range by retrieving and refocusing the complex wavefront back-scattered by point sources illuminated by low-coherence IR light.

Sculpting axial characteristics of incoherent imagers by hybridization methods

Axial resolving power (ARP) is one of the cornerstones of imaging systems. In conventional imaging systems, changing ARP by changing the numerical aperture affects also lateral resolving power (LRP). It is highly desirable to change ARP independent of LRP. Recently, incoherent digital holography (IDH) techniques were developed using sparse ensembles of Bessel, Airy and self-rotating beams that allow tuning ARP independent of LRP. In the above studies, the ARP was tuned by controlling the randomness which resulted in noisy reconstructions. In this study, we proposed and demonstrated two INCoherent Hybrid Imaging Systems (INCHIS) using a Bessel and spherical beam to change the ARP between the limits of Bessel and spherical beam independent of LRP. The first hybridization technique INCHIS-H1 requires pre-engineering of multifunctional phase masks using a recently developed modified Gerchberg-Saxton algorithm and an active device such as a spatial light modulator. The second hybridization technique INCHIS-H2 can be implemented using both active as well as passive optical elements with lens and axicon functions and the ARP is changed digitally after optical recording. While INCHIS-H1 requires pre-engineering of phase masks to change ARP like any conventional imaging system, the capability in INCHIS-H2 to change ARP post-recording opens a new pathway in imaging technology. Simulation results and proof-of-concept experimental results are presented. A recently developed Lucy-Richardson-Rosen algorithm has been used for image reconstruction for the above cases. We believe that the developed hybridization methods will revolutionize the field of IDH, computational imaging, computer vision and microscopy.

Depth formulation assessment of 1D light field display using self-interference incoherent digital holography

Light field display based on a lenticular lens is currently the most commercially available three-dimensional (3D) display system that can only provide one-dimensional (1D) parallax. In this paper, we outline the criteria for evaluating the voxel formulation of a 1D light field display system and experimentally measure its expressible depth range using an incoherent holographic camera. We use self-interference incoherent digital holography with a geometric phase lens to obtain the phase profile of the light field. To analyze the characteristic of the light field display, we reconstruct the incoherent hologram and apply the autofocus algorithm to evaluate the sharpness of formulated light field.

High-speed phase-shifting incoherent digital holography (invited)

We propose high-speed incoherent digital holography with a recording speed of 1,000 fps, which is designed for the three-dimensional (3D) motion-picture measurement of moving objects with high temporal resolution. We adopt single-shot phase-shifting incoherent digital holography, a high-speed polarization-imaging camera system, and a palm-sized self-interference interferometer designed for spatially and temporally incoherent light, to implement a high-speed phase-shifting incoherent digital holography system. High-speed four-dimensional (4D) (3D and time) measurement capability is experimentally demonstrated, using the constructed incoherent digital holography system set on a wagon and a daily-use white-color light-emitting diode.

Enhanced design of multiplexed coded masks for Fresnel incoherent correlation holography

Fresnel incoherent correlation holography (FINCH) is a well-established incoherent digital holography technique. In FINCH, light from an object point splits into two, differently modulated using two diffractive lenses with different focal distances and interfered to form a self-interference hologram. The hologram numerically back propagates to reconstruct the image of the object at different depths. FINCH, in the inline configuration, requires at least three camera shots with different phase shifts between the two interfering beams followed by superposition to obtain a complex hologram that can be used to reconstruct an object’s image without the twin image and bias terms. In general, FINCH is implemented using an active device, such as a spatial light modulator, to display the diffractive lenses. The first version of FINCH used a phase mask generated by random multiplexing of two diffractive lenses, which resulted in high reconstruction noise. Therefore, a polarization multiplexing method was later developed to suppress the reconstruction noise at the expense of some power loss. In this study, a novel computational algorithm based on the Gerchberg-Saxton algorithm (GSA) called transport of amplitude into phase (TAP-GSA) was developed for FINCH to design multiplexed phase masks with high light throughput and low reconstruction noise. The simulation and optical experiments demonstrate a power efficiency improvement of ~ 150 and ~ 200% in the new method in comparison to random multiplexing and polarization multiplexing, respectively. The SNR of the proposed method is better than that of random multiplexing in all tested cases but lower than that of the polarization multiplexing method.

Real-time noise-free inline self-interference incoherent digital holography with temporal geometric phase multiplexing

In this paper, we propose a real-time incoherent digital holographic (IDH) recording system free from bias and twin-image noises. A motionless three-step polarization-encoded phase-shifter operating at 99 Hz is realized with two electrically controllable birefringence-mode liquid crystal cells operating in tandem with a geometric phase lens and polarizers. Based on the proposed optical configuration, a coaxial straight-line self-interference IDH recording system is devised. Notably, the elimination of bias and twin-image noise from three phase-shifted images is demonstrated as a proof of concept. Moreover, complex-valued holographic video acquisitions with a resolution greater than 20 megapixels are demonstrated, with an effective acquisition frequency of 33 Hz.

In-line and off-axis polarization-selective holographic lenses recorded in azopolymer thin films via polarization holography and polarization multiplexing.

Polarization-selective diffractive in-line and off-axis lenses are recorded in azopolymer thin films using polarization holography. A simple, yet efficient, and to the best of our knowledge, new method is used to suppress the surface relief grating formation and to improve the polarization properties of the lenses. The in-line lenses are converging for right circularly polarized (RCP) light and diverging for left circularly polarized (LCP) light. Bifocal off-axis lenses are recorded by polarization multiplexing. By rotating the sample at 90° between the exposures, the two focal points of these lenses are located in orthogonal directions O x and O y, so we can refer to these novel lenses as 2D bifocal polarization holographic lenses. The light intensity in their focuses depends on the reconstructing light polarization. According to the recording scheme, they can either reach maximum intensities simultaneously (for LCP or RCP), or alternatively, one of them can be at maximum for LCP, while the other for RCP. These lenses may be used as polarization controllable optical switches, in the field of self-interference incoherent digital holography or for other photonics applications.

Simultaneous Capturing Technique of Holograms for Videography with Incoherent Digital Holography

太陽光や発光ダイオードなど身近に存在するインコヒーレント光を使って高精細な3次元情報を動的に取得することを目指し，インコヒーレントディジタルホログラフィー（IDH: Incoherent Digital Holography）の複数ホログラムの一括撮影技術として空間分割幾何位相シフト法を提案してきた．本手法では，位相格子による光の回折現象を応用して4枚のホログラムを空間的に分割して形成させ，円偏光の幾何位相により各ホログラムに異なる位相シフト量を付与できる．したがって，本手法により被写体の3次元情報を含んだ位相を検出するための複数ホログラムを一括に撮影できる．奥行き方向の異なる距離に配置された二つの動的な被写体を撮影する原理検証実験により，本手法の有効性を実証した．本論文では，空間分割幾何位相シフト法を導入したIDHの基本原理を概説し，IDHの動画像撮影に向けた研究状況を紹介する．

Optical Reconstruction of 3D Information Acquired by Incoherent Digital Holography

Optical Reconstruction of 3D Information Acquired by Incoherent Digital Holography

Interferenceless incoherent digital holography with binary coded apertures optimized using direct binary search

Coded aperture correlation holography offers 3D imaging with improved lateral and axial resolutions. This study is an additional advancement in the line of imaging systems with a pseudorandom coded aperture. Starting with the coded aperture correlation holography system implemented on an incoherent on-axis interferometer, we proposed interferenceless and lensless versions of the system. In the present study, we propose replacing the multi-values phase aperture mask with a binary mask. Two binary masks synthesized iteratively are used in two camera shots. Each mask is obtained from an iterative optimization process known as direct binary search, where the optimized cost function is the peak-to-background ratio of a reconstructed point object. Overall, the system demonstrates a lower background noise compared to other methods, enabling 3D imaging capability with only two camera shots, a substantial improvement in comparison to the many shots in the original systems. Using binary masks might extend the usefulness of the coded aperture holography for new regions in the electromagnetic spectrum other than the visual band, as of X-ray and THz bands.

Roadmap of incoherent digital holography

This roadmap article focuses on spatially incoherent digital holography (IDH). Representative IDH methods such as optical scanning holography (OSH), Fresnel incoherent correlation holography (FINCH), coded aperture correlation holography (COACH), IDH with a Fresnel zone aperture, and IDH with an interferometer along with a state-of-the-art optical device are introduced as modern IDH methods. We describe these IDH techniques with applications of three-dimensional (3D) imagers, 3D thermography, and 3D microscopy.

Compensation for reconstructed image distortion using camera model with lens distortion in incoherent digital holography

Compensation for reconstructed image distortion using camera model with lens distortion in incoherent digital holography