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Full-field swept-source optical coherence tomography (FF-SS-OCT) and laser Doppler holography (LDH) are two holographic imaging techniques presenting unique capabilities for ophthalmology. We report on interlaced FF-SS-OCT and LDH imaging with a single instrument. Effectively, retinal blood flow and pulsation could be quasi-simultaneously monitored. This instrument holds potential for a wide scope of ophthalmic applications.

Augmented reality (AR) near-eye displays (NEDs) are emerging as the next-generation display platform. The existing AR NED only present one single video channel at a time, same as traditional media such as TVs and smartphones. In this Letter, to the best of our knowledge, we propose for the first time a multi-channel holographic retinal projection display (RPD), which can provide multi-channel image sources simultaneously, thus greatly increasing the information content. Due to the superposition capacity of a hologram, multiple images are projected to different viewpoints simultaneously through multiple spherical wave encoding, so that the viewer can switch among playing channels very fast through eye rotation. A full-color dynamic multi-channel holographic near-eye display is demonstrated in the optical experiment. The proposed method provides a good prospect that the future AR glasses can play dozens of video channels in parallel, and the user can switch among channels freely and efficiently just through a simple eye rotation.

A Maxwellian display presents always-focused images to the viewer, alleviating the vergence-accommodation conflict (VAC) in near-eye displays (NEDs). Recently, many methods of improving its limited eyebox have been proposed, among which viewpoint replication has attracted a lot of attention. However, double-image, blind-area, and image-shift effects always happen in typical eyebox-replication Maxwellian NEDs when the eye moves between the replicated viewpoints, which prevents these NEDs from being applied more widely. In this Letter, we propose a method for designing a holographic Maxwellian NED system with continuous eyebox replication as well as flexible interval adjustment by changing the projection angles of the reconstructed images. Thus, holograms corresponding to the positions of different viewpoints are calculated to match the interval of the replicated viewpoints with the human pupil diameter, making it possible to eliminate or alleviate double-image or blind-area effects. Also, seamless viewpoint conversion in the eyebox is achieved by aligning the images of adjacent viewpoints on the retina via hologram pre-processing independently. These effects are verified successfully in optical experiments and have the potential to be applied in near-eye three-dimensional displays without VAC.

We present an erratum to our Letter [Opt. Lett. 46, 4694 (2021)10.1364/OL.432135]. This erratum corrects an unintended error in the labels of Figs. 5(h)–5(j). The corrections have no influence on the results and conclusions of the original Letter.

Here, we propose a double-face copper-cladded meta-hologram that can efficiently manipulate the amplitude of electromagnetic waves in both transmission and reflection spaces, depending on the polarization state of the incident electromagnetic wave. The proposed meta-hologram is validated by encoding the transmission–reflection amplitude information of two independent images into a single metasurface. The holographic images obtained from measurements agree qualitatively with simulation results. The proposed metasurface presents a novel, to the best of our knowledge, scheme for electromagnetic wavefront control in the whole space and overcomes the limitations of narrow frequency band operation.

Terahertz (THz) phase imaging is widely spreading in various scenarios, among which full-field phase distributions are commonly retrieved by digital holography or ptychography. In this Letter, the transport of the intensity equation reconstruction method is applied into the THz band. An algorithm named the lensless US-transport of intensity equation (TIE) is proposed to accommodate to an in-line configuration. The object phase is retrieved by primarily conducting iterations between the axial intensity derivative and the phase distribution at the recording plane and subsequent backward diffraction propagation. This method is applicable to both isolated and extended weakly absorbing samples with higher reconstruction quality and remarkably less time cost than holographic phase retrieval algorithms. It can also be attempted in other non-interferometric geometries or using low-cost partially coherent THz sources, which significantly broaden the application scope of THz phase imaging.

We adopted an unpaired neural network training technique, namely CycleGAN, to generate bright-field microscope-like images from hologram reconstructions. The motivation for unpaired training in microscope applications is that the construction of paired/parallel datasets is cumbersome or sometimes not even feasible, for example, lensless or flow-through holographic measuring setups. Our results show that the proposed method is applicable in these cases and provides comparable results to the paired training. Furthermore, it has some favorable properties even though its metric scores are lower. The CycleGAN training results in sharper and—from this point of view—more realistic object reconstructions compared to the baseline paired setting. Finally, we show that a lower metric score of the unpaired training does not necessarily imply a worse image generation but a correct object synthesis, yet with a different focal representation.

Designing a color hologram with conventional metasurfaces usually resorts to a supercell strategy or single-sized approach with different incident angles. However, these designs still have their own drawbacks that need to be further solved. Herein, we show a new, to the best of our knowledge, single-sized strategy to design full-color geometric meta-holograms by utilizing the conjugation property of two circularly polarized lights with opposite handedness and diffraction dispersion. The experimentally captured holographic color images are reconstructed with high quality and without cross talk, which agrees well with our theoretical prediction. Moreover, only with an appropriate combination of wavelength and polarization state can color images be observed accurately. Our strategy provides a simple and effective approach for full-color meta-holography and offers significant potential in image display, information storage, etc.

In this Letter, we introduce a computer-generated hologram (CGH) optimization technique that can control the randomness of the reconstructed phase. The phase randomness significantly affects the eyebox size and depth of field in holographic near-eye displays. Our proposal is to synthesize the CGH through the sum of two terms computed from the target scene with a random phase. We set a weighting pattern for summation as the optimization variable, which enables the CGH to reflect the random phase during optimization. We evaluate the proposed algorithm on single-depth and multi-depth contents, and the performance is validated via simulations and experiments.

A lensless full-color holographic Maxwellian near-eye display using a single amplitude-type spatial light modulator is proposed in this Letter. The color holographic image is directly projected onto the retina without any eyepiece. The color crosstalk is clearly separated from the signal in the space owing to the encoded spherical wave and carrier wave. An aperture numerical filter and a real polarized filter are used at the pupil plane to accurately stop the crosstalk light. A high-quality dynamic speckless color holographic image was produced in the mid-air within a specific depth range. The horizontal eyebox expansion is achieved simply through multiple spherical wave encoding and verified through an optical experiment. The proposed display is compact and promising as the augmented reality near-eye display.

We propose a compact tomographic near-eye display by combining a micro–electro–mechanical systems (MEMS) scanning mirror device, focus tunable lens, and a single light-emitting diode source. A holographic optical element was used to elaborately focus the light source into the MEMS scanning mirror while providing further miniaturization. We implemented a drastically downsized multifocal display system that expresses a depth range of 4.8 D with eight focal planes by synchronizing these modules. Furthermore, the planar images are optimized to achieve correct retinal scenes at each accommodation state. The simulated and experimental results verify that the suggested near-eye display system can provide three-dimensional virtual images while showing physical feasibility.

Multilayered diffraction gratings are an essential component in many optical devices due to their ability to engineer light. We propose a first-order optimization strategy to maximize diffraction efficiencies of such structures by a fast approximation of the underlying boundary integral equations for polarized electromagnetic fields. A parametric representation of the structure interfaces via trigonometric functions enables the problem to be set as a parametric optimization one while efficiently representing complex structures. Derivatives of the efficiencies with respect to geometrical parameters are computed using shape calculus, allowing a straightforward implementation of gradient descent methods. Examples of the proposed strategy in chirped pulse amplification show its efficacy in designing multilayered gratings to maximize their diffraction efficiency.

In this Letter, we present a holography-based structured light illumination (SLI) method to enhance the resolution of widefield temporal focusing microscopy (TFM). In the system, a digital micromirror device is employed to simultaneously disperse the incoming femtosecond laser to induce temporal focusing at the focal plane and generate designed structured patterns via a Lee hologram. As the generated structured patterns do not contain the zeroth order beam, it improves the contrast and modulation frequency. Mathematical models have been derived to calculate the electric fields at the focal plane and to explain the effects of improved optical cross-sectioning capability. Imaging experiments have been devised and performed on fluorescent beads and mouse kidney sections; the results demonstrate enhanced axial confinement and improved suppression of out-of-focus fluorescence. The new SLI method realizes high-resolution TFM and can be readily applied to other microscopy platforms for biophotonics applications.

Learning-based computer-generated holography (CGH) provides a rapid hologram generation approach for holographic displays. Supervised training requires a large-scale dataset with target images and corresponding holograms. We propose an autoencoder-based neural network (holoencoder) for phase-only hologram generation. Physical diffraction propagation was incorporated into the autoencoder’s decoding part. The holoencoder can automatically learn the latent encodings of phase-only holograms in an unsupervised manner. The proposed holoencoder was able to generate high-fidelity 4K resolution holograms in 0.15 s. The reconstruction results validate the good generalizability of the holoencoder, and the experiments show fewer speckles in the reconstructed image compared with the existing CGH algorithms.

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.

We propose astigmatic dual-beam interferometric particle imaging (ADIPI) to simultaneously measure the three-dimensional (3D) position and size of spherical metal droplets. A theoretical model reveals that the orientation and spacing of the ADIPI fringes generated from the two reflections propagating through an astigmatic imaging system relate to the depth position and size, respectively. Proof-of-concept experiments on micron-sized gallium droplets are performed, and the tilted fringes in elliptical patterns are observed in the ADIPI interferogram, confirming theoretical predictions. Droplet 3D position and size are determined with ADIPI, and the relative discrepancies are within 5% and 2% compared to those with a dual-view digital inline holography system, demonstrating the feasibility and high accuracy of ADIPI.

Efficient light harvesting is essential for advanced photonic devices. Complex micro/nano surface relief structures can be produced via light-triggered mechanical movement, but limited in organic active molecular units. In this Letter, we propose to embed noble-metal particles into light-inactive polyvinyl alcohol matrix to construct a light harvesting system driven by plasmon for inscription of surface relief gratings. Ultra-small-sized silver nuclei are generated in the polymer by pre-thermal treatment, acting as an accelerator for the subsequent photoinduced particle growth, hydrogen group cleavage, and matrix softening. Based on such properties, a complex plasmonic array carrying ultra-high-density information is achieved with peristrophic multiplexing holography. This Letter paves a bright way to realize data storage, information encryption, and optical microcavity.

We propose a phase-shifting interferometry technique using only two in-line phase-shifted self-interference holograms. There is no requirement for additional recording or estimation in the measurement. The proposed technique adopts a mathematical model for self-interference digital holography. The effectiveness of the proposed technique is demonstrated by experiments on incoherent digital holographic microscopy and color-multiplexed fluorescence digital holography with computational coherent superposition. Two-color-multiplexed four-step phase-shifting incoherent digital holography is realized for the first time, to the best of our knowledge, using the proposed technique.

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.

Digital optical phase conjugation (DOPC) can be applied for light-field focusing and imaging through or within scattering media. Traditional DOPC only recovers the phase but loses the polarization information of the original incident beam. In this Letter, we propose a dual-polarization-encoded DOPC to recover the full information (both phase and polarization) of the incident beam. The phase distributions of two orthogonal polarization components of the speckle field coming from a multimode fiber are first measured by using digital holography. Then, the phase distributions are separately modulated on two beams and their conjugations are superposed to recover the incident beam through the fiber. By changing the phase difference or amplitude ratio between the two conjugate beams, light fields with complex polarization distribution can also be generated. This method will broaden the application scope of DOPC in imaging through scattering media.

A holographic super multi-view (SMV) Maxwellian display based on flexible wavefront modulation is proposed for the first time, to the best of our knowledge. It solves the issue that the previous holographic Maxwellian displays could not provide depth cues for monocular vision. Different from the previous methods, two or more parallax images are multiplied by quadric phase distributions and converged to the viewpoints existing in the pupil to provide 3-D vision. A time division method is proposed to eliminate the cross talk caused by the coherence of different spherical waves. Experiments demonstrate that the proposed method can accurately reconstruct images at different depth without cross talk. The proposed method inherits the previous holographic Maxwellian display's advantages of flexible viewpoint position adjustment and large depth of field (DOF). Superior to geometric optics based SMV displays, the proposed system is compact without lens aberration since only a single spatial light modulator (SLM) is needed without any additional optical elements.

Focimeters, especially manual versions, are the most used ophthalmic devices for dioptric power measurement in optometric clinical care. In the particular case of progressive addition lenses (PALs), they are used to determine far/near vision correction powers, but the user/clinician needs to know at which part of the PAL the measurement must be taken. For this reason, PALs have permanent engravings acting as reference marks to define the far/near vision areas for every PAL design. However, for several reasons these engravings are often difficult to localize and identify, making an accurate dioptric power determination difficult. In this Letter, we present an adaptation of the Gabor holographic principle to a manual focimeter and describe the methodology for the correct localization, visualization, and marking process of the reference engravings in PALs. Experimental results considering different types of PALs are included and the main limitations of the technique are also discussed.

We present a method of single-frame reconstruction in off-axis digital holography with Kronecker-product interpolation to maximize spatial-frequency extraction. The Kronecker-product interpolation operated on a one-frame off-axis digital hologram can generate several aliasing spectra in its Fourier domain, where the zero-order aliasing spectra in the extrapolation region can be suppressed effectively. After adding all aliasing spectrum regions and substituting each aliasing spectrum in place with their sum, spectrum interception with a larger scope for filtering can be made in one of the aliasing spectrum regions. The experimental results demonstrate that the method is valid to improve the resolution in off-axis digital holography.

Three-dimensional (3D) imaging of living organisms requires fine optical sectioning and high-speed image acquisition, which can be achieved by light sheet fluorescence microscopy (LSFM). However, orthogonal illumination and detection arms in the LSFM system make it bulky. Here, we propose and demonstrate the application of a volume holographic optical element (photopolymer-based volume holographic grating) for designing a compact LSFM system, called a volume holographic LSFM (VHLSFM). Using the VHLSFM, we performed in vivo imaging of Caenorhabditis elegans (C. elegans) and observed high-contrast optically sectioned fluorescence images of the oocytes and embryonic development in real time for 3D imaging.

Optical super-oscillatory lenses based on planar micro/nano structures have been demonstrated as promising alternatives for shaping wavefronts of light and realizing super-resolution images in a NA-limited optical system. However, as the super-oscillatory foci originated from the delicate interference of the light, the change of the parameters might destroy the hotspots, such as the incident wavelength. Here, a multiwavelength achromatic super-oscillatory metasurface (ASOM) is proposed through simultaneously controlling distinct wavelength-dependent wavefronts. The constructed multiwavelength ASOM is then verified numerically, and the foci are precisely formed at the same axial plane for the design wavelengths with resolution beyond the diffraction limit. We expect that our proposed multiwavelength controllable method will give more freedom for the designs of planar and lightweight components, which would be useful in optical applications, such as data storage, super-resolution imaging, holography, etc.

Dynamic self-assembly of micropillars has found wide applications in targeted trapping, micro-crystallization and plasmonic sensing. Yet the efficient fabrication of micropillars array with high flexibility still remains a grand challenge. In this Letter, holographic femtosecond laser multi-foci beams (fs-MFBs) based on a spatial light modulator (SLM) is adopted to efficiently create micropillars array with controllable geometry and spatial distribution by predesigning the computer-generated holograms (CGHs). Based on these micropillars array, diverse hierarchical assemblies are formed under the evaporation-induced capillary force. Moreover, taking advantage of the excellent flexibility and controllability of fs-MFBs, on-demand one-bead-to-one-trap of targeted microspheres at arbitrary position is demonstrated with unprecedentedly high capture efficiency, unfolding their potential applications in the fields of microfluidics and biomedical engineering.

Mueller matrix microscopy (MMM) is a powerful approach to probe microstructural and optical information of many important specimens (e.g., tissue and bacteria), which otherwise cannot be obtained directly from intensity or spectral images. Achieving high lateral resolution in MMM, similar to other microscopy approaches, remains a challenge. Here, we extend the idea of microsphere (MS) -assisted microscopy into MMM toward resolution-enhanced polarimetric imaging. The goal is achieved by insertion of a transparent MS in the working distance of the imaging microscope objective in the optical train of an MMM system. We experimentally show that an MS close to the sample in MMM may increase the resolution beyond the intrinsic diffraction limit of the system by redirecting the higher spatial frequencies of the sample into the acceptance cone. In order to be a case in point, the experiment is conducted on a standard holographic diffraction grating with 1 µm line-width, which is beyond the diffraction limit of a 10 × objective. Two-dimensional images of the Mueller matrix and some of the widely used quantitative polarimetric parameters of the sample are calculated and compared in the two cases before and after insertion of MS. The proposed arrangement is easy to implement and has the potential to serve as a high-resolution polarimetric microscope for visualizing the polarization characteristics of the microscopic objects.

In this Letter, a deep learning solution (Y4-Net, four output channels network) to one-shot dual-wavelength digital holography is proposed to simultaneously reconstruct the complex amplitude information of both wavelengths from a single digital hologram with high efficiency. In the meantime, by using single-wavelength results as network ground truth to train the Y4-Net, the challenging spectral overlapping problem in common-path situations is solved with high accuracy.

Optical, spatial, or temporal multiplexing is a well-known approach to optimize the performance of imaging systems. Following the recent discovery about the capability to record a coherent hologram in an interferenceless working mode, we propose a motionless method to spatially multiplex more than one hologram in a single camera exposure. Using the rather simple multiplexing framework based on coded aperture correlation holography, we effectively increase the acquisition rate of dynamic scenes and the holographic data compression by two-fold. Quantitative or qualitative phase microscopy and acquisition of a bipolar hologram from a single camera shot, experimentally confirm the applicability of the suggested technique.

Optical scanning holography (OSH) is an attractive technique since 3D information can be obtained with a single pixel detector. However, OSH requires an interferometer, scanning architecture, and a frequency shifter to scan a time-varying Fresnel zone plate (FZP), which makes the optical setup complicated. To reduce the complexity, the polarization sensitivity of a spatial light modulator (SLM) is applied. The proposed method implements a time-varying FZP with an in-line optical setup by using only an SLM. Observing results for a USAF pattern and a fluorescent bead reveals the feasibility of the new motionless holographic 3D imaging technique.

Advances in human brain imaging technologies are critical to understanding how the brain works and the diagnosis of brain disorders. Existing technologies have different drawbacks, and the human skull poses a great challenge for pure optical and ultrasound imaging technologies. Here we demonstrate the feasibility of using ultrasound-modulated optical tomography, a hybrid technology that combines both light and sound, to image through human skulls. Single-shot off-axis holography was used to measure the field of the ultrasonically tagged light. This Letter paves the way for imaging the brain noninvasively through the skull, with optical contrast and a higher spatial resolution than that of diffuse optical tomography.

A reconstruction method for multilevel complex encoded data-pages is proposed to increase the recording density of computer-generated-hologram-based holographic data storage by using off-axis digital holography. Although the detection process is based on off-axis digital holography, the proposed method keeps the optical setup a simple and common-path configuration owing to the computer-generated holography. Five-level complex encoded data-pages can be experimentally reconstructed.

We report, to the best of our knowledge, the first optical trapping experimental demonstration of microparticles with frozen waves. Frozen waves are an efficient method to model longitudinally the intensity of nondiffracting beams obtained by superposing copropagating Bessel beams with the same frequency and order. Based on this, we investigate the optical force distribution acting on microparticles of two types of frozen waves. The experimental setup of holographic optical tweezers using a spatial light modulator has been assembled and optimized. The results show that it is possible to obtain greater stability for optical trapping using frozen waves. The significant enhancement in trapping geometry from this approach shows promising applications for optical tweezers micromanipulations over a broad range.

Optical scanning holography requires interference optics, which separates a laser beam into two paths and recombines the two path beams after being modulated spatially and temporarily. This requires high accuracy and stability of the apparatus with a highly coherent light source. In this Letter, we propose a coaxial scanning holography (CSH) capable of realizing scanning holography with high stability and low complexity by forming a scanning beam in a single optical path using a geometrical phase shift. An experimental verification of the CSH by optical acquisition and subsequent reconstruction of the hologram is reported.

In this Letter, we propose a new (to the best of our knowledge), promising concept of a hybrid femtosecond (fs) laser processing method composed of single-point scanning and holographic light modulation fabrication for manufacturing a tunable-size microtrap chip. The hybrid method not only ensures key microfluidic device precision but also greatly improves the fabrication speed. By using a new asymmetry-bracket-shaped microtrap design with a mechanical strain stretching method, real-time size-tunable trapping is obtained, and a 100% particle trapping retention is realized, ignoring the flow fluctuation. Finally, the microtrap array is successfully applied to trap single yeast cells and hold them for ∼ 10 h without escaping.

The conventional computer-generated hologram reconstructing photorealistic three-dimensional (3D) images based on ray-wavefront conversion has the disadvantage of spatio-angular resolution trade-off. In this Letter, we propose for the first time, to the best of our knowledge, a computer-generated photorealistic hologram without spatio-angular resolution trade-off based on the additive compressive light field (CLF) approach. The original light field is compressed into multiple layer images through numerical optimization based on the additive light field principle. Then, by independently calculating the wave propagation from each layer image to the hologram plane and adding them together, a CLF hologram is generated. Since the CLF information is presented through a holographic method, the advantage of high resolution in CLF is preserved while the limitation of the number of physically stacked layers (such as liquid crystal displays) is removed, leading to higher quality, larger depth of field, and higher brightness compared with a conventional CLF display. The proposed method is verified with a photorealistic optical experiment.

We present an algorithmic approach for holographic shaping of partially coherent light, which is described by a mode expansion containing thousands of individual modes. Using gradient descent and algorithmic differentiation, our algorithm is able to find a set of axially separated phase patterns such that each mode undergoes an individually optimized transformation with respect to the formation of a user-defined target intensity distribution. We demonstrate numerically and experimentally that a tandem of two phase patterns can achieve any intensity profile transformation with good accuracy.

We propose a novel, to the best of our knowledge, waveguide-type optical see-through Maxwellian near-eye display for augmented reality. A pin-mirror holographic optical element (HOE) array enables the Maxwellian view and eye-box replication. Virtual images with deep depth of field are presented by each pin-mirror HOE, alleviating the discrepancy between vergence and accommodation distance. The compact form factor is achieved by the thin waveguide and HOE couplers.

Coded aperture correlation holography (COACH) needs the point spread function (PSF) for image reconstruction. Utilizing a pinhole to generate a point light source is the most frequently adopted method for measuring PSF, which, however, has significant issues to resolve. One of the problems is that the resolution of the reconstructed result is limited by the cutoff frequency of the pinhole. The other is that the far-field PSF is undetectable because the amount of light illuminance decreases with the distance. In this work, we present a method for recording the PSF based on wavefront modulation. By modulating a plane wave with both the carrier spherical wave and the coded phase mask, we obtain a virtual point spread function (VPSF) that is used for image reconstruction. It is shown that the resolution of reconstructed results is not limited by the pinhole. We experimentally demonstrate high-resolution reconstruction by the VPSF.

An Airy beam can be used to implement a non-diffracting self-bending point-spread function (PSF), which can be utilized for computational 3D imaging. However, the parabolic depth-dependent spot trajectory limits the range and resolution in rangefinding. In this Letter, we propose a novel pupil-phase-modulation method to realize a non-diffracting linear-shift PSF. For the modulation, we use a focus-multiplexed computer-generated hologram, which is calculated by multiplexing multiple lens-function holograms with 2D sweeping of the foci. With this method, the depth-dependent trajectory of the non-diffracting spot is straightened, which improves the range and resolution in rangefinding. The proposed method was verified by numerical simulations and optical experiments. The method can be applied to laser-based microscopy, time-of-flight rangefinding, and so on.

A new type of functional optical microscope system called three-dimensional (3D) stimulation and imaging-based functional optical microscopy (SIFOM) is proposed, to the best of our knowledge. SIFOM can precisely stimulate user-defined targeted biological cells and can simultaneously record the volumetric fluorescence distribution in a single acquisition. Precise and simultaneous stimulation of fluorescent-labeled biological cells is achieved by multiple 3D spots generated by digital holograms displayed on a phase-mode spatial light modulator. Single-shot 3D acquisition of the fluorescence distribution is accomplished by common-path off-axis incoherent digital holographic microscopy in which a diffraction grating with a focusing lens is displayed on another phase-mode spatial light modulator. The effectiveness of the proposed functional microscope system was verified in experiments using fluorescent microbeads and human lung cancer cells located at various defocused positions. The system can be used for manipulating the states of cells in optogenetics.

A new, to the best of our knowledge, configuration of common-path off-axis digital holography is proposed for simultaneous evaluation of out-of-plane and in-plane displacements of the vibrating object. The object is illuminated from two different directions, and each illumination interferes with its corresponding reference beam generated near the object, resulting in two independent holograms that are spatially multiplexed in a single camera image. Two multiplexed holograms, at undeformed and deformed states of the object, are recorded and processed to obtain the out-of-plane and in-plane displacements simultaneously. The proposed digital holographic system has the advantage of a simple and compact optical setup, is less sensitive to environmental disturbances, and has high temporal phase stability. The two-dimensional ( z , x ) full-field amplitude and phase vibration analysis of a perfect specularly reflecting surface are also demonstrated by the proposed holographic system. The experimental results authenticate the feasibility of the proposed system and reveal its unique advantages. The proposed digital holographic system, owing to simple and compact geometry and providing several advantages over other two-channel holographic systems, may find a wide range of applications in investigating real-time dynamic phenomena.

We propose a compact polarization-resolved common-path digital holography for measuring the polarization distribution of a light field dynamically with high temporal stability. The designed experimental setup allows simultaneously recording, in a common-path manner, two holograms carrying the complex amplitude information of two orthogonal polarization components of the light field. Based on the theory of the Pancharatnam–Berry phase to retrieve the full Stokes parameters of the light field, we demonstrate the experiments with polarized optical elements, stressed glass plate, and micrometer-sized liquid crystal droplet. The measurement results verify the method’s high accuracy and stability, and the capability of measuring light fields with sizes ranging from centimeters to micrometers. Owing to the stable and compact optical path structure, this method is conducive to instrumentation and is expected to find wide applications in many fields.

Computer-generated holography suffers from high diffraction orders (HDOs) created from pixelated spatial light modulators, which must be optically filtered using bulky optics. Here, we develop an algorithmic framework for optimizing HDOs without optical filtering to enable compact holographic displays. We devise a wave propagation model of HDOs and use it to optimize phase patterns, which allows HDOs to contribute to forming the image instead of creating artifacts. The proposed method significantly outperforms previous algorithms in an unfiltered holographic display prototype.

Vulnerability analysis of optical encryption schemes using deep learning (DL) has recently become of interest to many researchers. However, very few works have paid attention to the design of optical encryption systems using DL. Here we report on the combination of the holographic method and DL technique for optical encryption, wherein a secret image is encrypted into a synthetic phase computer-generated hologram (CGH) by using a hybrid non-iterative procedure. In order to increase the level of security, the use of the steganographic technique is considered in our proposed method. A cover image can be directly diffracted by the synthetic CGH and be observed visually. The speckle pattern diffracted by the CGH, which is decrypted from the synthetic CGH, is the only input to a pre-trained network model. We experimentally build and test the encryption system. A dense convolutional neural network (DenseNet) was trained to estimate the relationship between the secret images and noise-like diffraction patterns that were recorded optically. The results demonstrate that the network can quickly output the primary secret images with high visual quality as expected, which is impossible to achieve with traditional decryption algorithms.

Conventional holographic display suffers from the conjugate light issue. In this Letter, we propose to efficiently extend the eyebox of holographic Maxwellian near-eye display by encoding the conjugate wavefront as the multiplication of plane wave phase with the target image. It is interesting that after being focused by the lens, the generated conjugate viewpoints also present erect virtual images with the same image quality as the signal viewpoints. Multiple plane wave encoding is used for eyebox extension, and, because of the utilization of conjugate light, the effect of eyebox extension is doubled. That is, the space bandwidth of the amplitude-type hologram is fully used. A speckless holographic image is produced in mid-air with high quality within a large depth range. The proposed display is compact and promising for the augmented reality near-eye display. Furthermore, it may inspire better solutions for the conjugate light issue of amplitude-type holography.