This PDF file contains the front matter associated with SPIE Proceedings Volume 11551 including the Title Page, Copyright information, and Table of Contents.

Holographic optical elements (HOEs) are very interesting optical devices based on the holography technique and have been spotlighted in the augmented reality (AR) application recently. The HOEs have optically see-through property due to their high angular-selectivity, which has an extensive potential to be employed as an image combiner for the AR devices. Various optical functions, such as reflection, lens and diffusing, can be implemented with thin-layer HOEs. This advantage can replace the conventional bulky optics with HOEs for a compact form factor. In addition, multi-functionality can be realized with multiplexed recording, and optical mass production is possible, which is especially useful for AR display systems.

Information retrieval from optical speckles is desired yet challenging. Insufficient sampling, especially in sub-Nyquist domain, of speckles significantly destroys the encoded information and correlations among these speckle grains. To address that, we trained a deep neural network to combat the physical imperfection: the sub-Nyquist sampled speckles (~14 below the Nyquist criterion) are interpolated up to a well-resolved level (322 times more pixels to resolve the same FOV) with smoothed morphology fine-textured, and more importantly, lost information retraced. With the FOV-resolution dilemma favorably overcome, it deepens our understanding of the scattering, enabling big and clear imaging in complex scenarios.

We apply deep learning (DL) to counter three key problems which may occur in single-pixel imaging (SPI) namely noise, appearance of ringing or pixelated artifacts due to undersampling, and effects of projector lens aberration or defocusing. We employ a multi-scale mapping based deep convolutional neural network (DCNN) architecture to rectify undesirable effects in a 96×96 target reconstruction produced by environmental or system conditions, and optical anomalies. We train the proposed DCNN on augmented experimental data as well as simulation data to achieve robust experimental performance. Experimental results on real targets (2D and 3D) demonstrate the superior performance of the proposed method compared to conventional SPI.

Deep learning has great potential in computational imaging. We propose to use three kinds of artificial neural networks in phase imaging works. An improved U-net is used to do phase unwrapping with a new phase dataset generation method and do phase imaging in an optical microscope with Transport of Intensity Equation (TIE). And then, Y-Net and Y4-Net are used to do single-wavelength and dual-wavelength digital holographic reconstruction, respectively.

We propose a short-path U-net model with average pooling in order to restore in-focus images of multiple transparent particles at ground truth z positions and simultaneously remove their zero-order images, conjugate images, the defocused images of the other particles, and the noise induced by the optical system in a volume. Subsequently, we obtain the lateral location and diameter of each particle in a fast way based on the nature of the particles’ shape; eventually acquire the particle density in the captured volume. The experimental results demonstrate that all sized particles including small– sized and relatively large-sized particles can be restored well by a short-path U-net model, and average pooling performs well when dealing with piece-wise pattern. The proposed scheme can distinguish as many particles as possible in a small volume with small reconstruction depth spacing, such as 50 μm.

Digital holographic imaging is able to reconstruct 3D or phase information of the object from a one-shot 2D lensless hologram. The inverse reconstruction of 3D particle field could be realized based on the deep convolutional neural network. The hologram of a single particle is spread throughout the detector. Deep convolutional neural network could perform particle feature extraction and obtain the 3D position of each particle. We propose a learning-based approach for 3D holographic particle imaging. A dense encoder-decoder U-net network is designed. Compared with the CNN-based U-net network and the residual connection-based U-net network, the proposed network can reduce the number of network parameters, increase the amount of information of each layer of particles, extract accurate particle characteristics, and improve robustness. The Dense-U-net is more efficient in the way it processes data and requires a less memory storage for the learned model.

Microplastics, which are a major source of pollution in the ocean, need to be accurately detected and monitored. However, the current detection approaches often require complex optical instrumentation and a long time for image processing. Furthermore, because of the difficulties of particle sampling, it is hard to collect a dataset with sufficient images and a balanced distribution. Digital holography, which is a non-destructive imaging method, is suitable for the in situ imaging. In this work, we propose a novel digital holography microplastics classification system which combines deep learning and generative adversarial networks. We experimentally show that our method yields a higher accuracy for microplastics classification and can efficiently reduce the imbalance ratio of the dataset. This method can be modified for other in situ image classification tasks that likewise suffer from a small and imbalanced distribution dataset.

We introduce a multi-branch model-based architecture for image reconstruction in lensless imaging. The structure consists of two learning branches, namely a physical model-based network, and a data-driven network. It uses intermediate outputs from the former as a prior for guiding the learning of the reconstruction neural network, which mimics the mapping between the reconstructed high-resolution images and raw images. We demonstrate that the proposed architecture offers a flexible combination of model-based methods and deep networks with superior reconstruction performance than methods using only an unrolled optimization network or pure deep neural networks for image reconstruction.

Graphene oxide (GO) is a precursor material for producing graphene. The electrical and optical properties of GO can be modified by reduction of the oxygen-containing groups. In this report, we have prepared graphene oxide polymers (GO-polymer) with different vol. % of GO and reduced the polymer by direct laser writing. We have found the refractive index modulation of the GO-polymer up to 10^(-1) for 15 vol.%.

In this paper, a non - color far - field ultra - focused surface plasma exciton nanostructure is proposed. The structure is composed of multiple rings and multiple grooves. The super oscillation effect of radial polarized light irradiation in concentric multi-annulus is produced. Multiple grooves scatter surface plasma polarons (SPPS) into free space at the nanoscale. The interaction between the nanometer superfocusing effect and the super oscillation effect can form different focal points between the near field and the far field. Finite-difference time-domain (FDTD) method was used to numerically calculate the focal length (FL), full width at half maximum (FWHM) and depth of focus (DOF). Achromatic nanoscale superfocus from near field to far field provides an application method for dynamic 3D imaging and multilayer optical storage in super-resolution display.

To Improve axial resolution of digital holographic microscopy, we optimized the light source based on the patterned quantum dots (QDs) film with blue LED. We tried to pattern the QDs laterally as a 2-D patterned QD film by photolithography and micro imprinting process to improve color conversion efficiency of QDs as well as keep narrow bandwidth, resulting in enhancing the optical intensity and axial resolution. Using the additional optical edge filters and relay optics, newly proposed light source of digital holography microscopy for QPI has resulted in the enhanced axial resolution to1.8μm and the increased optical signal.

By using the concept of picometer comb, picometer microscopy is proposed using picometer light fields, picometer measurement, picometer positioning, picometer feedback and locked-in to enhance the signal-to-noise ratio. The implementation of picomicroscopy in picometer accuracy is illustrated in a few configurations.

We have investigated the internal structure of materials by use of a digital acousto-optic holographic technique. The innovative technique is effective in detecting the internal structure information of functional gradient materials. The present visible-light-source-based digital holographic techniques are not able to detect the internal structure information of non-transparent objects and that motivates us to seek the ultrasound-based digital optical holography alternative. The characteristic model of functional gradient materials is modeled through finite element modeling software. The effects of material composition, shape and density on the ultrasound field distribution are simulated, which reveal the propagation pattern of the ultrasound in functional gradient materials as the shape, density and elastic modulus of the medium affect the acoustic properties. The dynamic changes of quantitative mapping relationship between the internal structural information and the sound field is also analyzed. Results indicate that the change is correlated with the internal structural information of the object. The simulation results provide useful quantifiable information for the subsequent research of digital acousto-optic holography to detect the internal structure of materials. Our research is applicable to various industrial problems where traditional digital holographic techniques alone fail to deliver solutions.

Phase sensitivity plays a vital role in accurately retrieving three-dimensional (3D) shape of diffused objects in fringe projection profilometry (FPP). With regard to traditional means that simply project horizontal or vertical fringe patterns, the fringe frequency and direction are not the best choice to acquire optimal sensitivity to depth variations. This talk will present a novel method to obtain 3D shape with high accuracy by combining the optimal fringe frequency and the optimal fringe direction (OFF + OFD). The simulated and actual experiments have been carried out to demonstrate that the proposed optimization method is feasible and effective in increasing phase sensitivity and measurement accuracy.

The accuracy of the asphere testing using computer-generated holograms (CGH) is determined by the precision of the diffractive pattern fabrication. In this paper, two methods for quality control of CGHs are presented. These methods are based on writing small marks, which have microgratings with 2-5 µm period. These marks consist of two parts, one of which is formed before the fabrication of CGH. The second one is embedded during the writing process of the main diffractive pattern. The shift between the first and second parts of the mark makes it possible to determine the drift of the positioning system for both coordinates.

Phase-shifting interferometry selectively extracting wavelength information has been proposed since 2013, which is called computational coherent superposition (CCS) of multiple wavelengths. In this proceeding, we apply CCS to self-interference incoherent holography and construct single-path, mechanical-motion-free, wavelength-multiplexed, incoherent multicolor digital holographic microscopy systems. Also, we numerically investigate quantum fluctuation in phase-shifting interferometry for the sensing of weak light such as natural light and nonlinear light. After that, we briefly discuss the difference between the digital holography systems with CCS and phase-shifting interferometry with a Bayer color image sensor.

We report on a single-shot phase detection method for holographic data storage systems using polychromatic reconstruction (PCR). In PCR, the multi-step interferometric measurements cannot be applied for signal phase detection, because the reconstructed image consists of the broad spectral components spatially distributed within the page. Our proposed method utilizes inter-pixel crosstalk caused by an aperture inserted in the Fourier plane of the input image, and does not require any interferometric measurements, like a four-step phase-shifting method. We have numerically investigated pixel error rates of phase-encoded signals in PCR, and confirm the validity of our proposed method.

We have proposed a band-extended angular spectrum method (BEASM) for the accurate and efficient diffraction calculation. The proposed BEASM has been used for a resolution-enhanced digital holographic imaging. By rearranging the sampling points of the transfer function in the spatial frequency domain according to the sampling theorem, more effective object spectrum can be transferred during the diffraction calculation which is the key of the numerical reconstruction in digital holography. Therefore, higher resolution imaging has been achieved thanks to the extension of the computational bandwidth. Both numerical simulation and optical experiments have been carried out to validate the proposed method.

Fringe pattern analysis is an essential step in optical techniques including the digital speckle pattern interferometry (DSPI), digital speckle shearing interferometry (DSPSI), digital holographic interferometry (DHI), moiré interferometry, and others. This step enables to evaluate the coded phase distribution related to a physical magnitude of the material under study such as deformation, displacement, refractive index, strain, temperature. Several methods have been proposed for the extraction of phase distribution such as phase-shifting techniques and other transform-based methods like Fourier, Hilbert, and wavelet transforms. In phase-shifting techniques, the intensity is sampled spatially or temporally, and the object should be stable during the acquisition of at least three frames. So, this technique is not suitable for the analysis of dynamic events. Recently, Riesz transform, two-dimensional extension of the Hilbert transform, has been exploited in several works including the phase evaluation. In this work, we present a variety of methods based on the Riesz transform for fringe pattern analysis. The analysis concerns the extraction of the encoded phase distribution from the recorded/processes fringe patterns obtained from the interferometric techniques and their horizontal and vertical phase derivatives. Using numerical simulation, we study the performance of these Riesz transform-based methods with a quantitative appraisal, and finally, the experimental application will be presented. The advantages and limitations of the Riesz transform-based methods will be discussed.

We introduce a novel feedback-based wavefront shaping algorithm “dynamic mutation algorithm (DMA)”, which has high adaptability and a unique recovery ability. The optimization is based on the real-time error rate, which implies how far the optimization has gone toward the theoretical optimal result. The phase map is dynamically mutated according to the instant optimization state. When it encounters alteration in the transmission matrix, the diminished focus can be recovered, which no other current algorithms can achieve as they are usually heavily based on previous iterative results. The new algorithm has the potential to boost many applications in unstable scattering environments.

Light is almost ideal to probe and treat biological tissues. Its applications, however, encounter an inevitable trade-off between resolution and penetration depth due to the strong scattering of light in tissue. Existing optical microscopies can seldom see beyond 1 mm beneath human skin. In this talk, we present our endeavors in the past years to achieve high-resolution optical focusing within or through thick biological tissue or tissue-like scattering media via optical wavefront shaping. We also show our preliminary results of applying wavefront shaping implementations towards temporal evolutional optogenetics with single neuron precision through brain skull. Further direction is also discussed.

In this presentation, we briefly review the fluorescence and the phase imaging techniques based on computational imaging such as digital holography and transport of intensity equation. These techniques uses an image sensor to capture the hologram or the intensity distribution and it enables more faster recording than the point-scanning methods. The presented techniques have also an advantage to refocus the images by applying an appropriate distance. Some experimental results are provided to show the effectiveness of the methods. Multimodal three-dimensional imaging is also presented.

This paper presents DMD-addressing based ptychographic phase microscopy (DA-PPM) and phase/fluorescence dual-modality imaging in DA-PPM. Compared with conventional ptychographic approaches, the imaging speed of DA-PPM is significantly enhanced by DMD based illumination selection, and is further enhanced by parallel illumination, i.e., lighting up parallelly multiple sub-areas in one shot. Furthermore, two-folds spatial resolution enhancement can be achieved in DA-PPM by incorporating structured illumination generated by DMD. Last but not least, phase/fluorescence dual-modality imaging will be performed in DA-PPM, providing for the same sample complementary information, including structural and functional information.

Compressive sensing (CS) has been used in in-line digital holography (DH) to eliminate the noise, especially the interference caused by twin image. In this work, we combine the two-step iterative shrinkage-thresholding (TwIST) algorithm in CS and autofocusing methods to accomplish high-resolution imaging from a single-exposure hologram. We preprocess all the images within a reconstruction distance through TwIST algorithm, and then evaluate the focal plane of the images according to the focusing functions including the Laplace operator and the absolute gradient operator, etc. The proposed method can not only effectively eliminate twin image to improve the imaging quality, but also perform unique advantages to estimate the in-focus distance in DH.

FZA imaging is one of the most promising lensless techniques because of its simple structure without calibration. The conventional image reconstruction methods are based on geometric optics model, then the error brought by diffraction degrades the imaging quality and limits the resolution. Here we quantitatively analyze the relationship between the width of FZA zone and the imaging resolution. The effects of illumination wavelength and the degree of coherence on image quality are also discussed. To improve the imaging quality, an image reconstruction method is proposed to minimize the influence of diffraction effect.

In this paper, the principle as well as the implementation of EPISM method are introduced firstly. In order to evaluate the reconstruction quality better, the imaging process of EPISM based holographic stereogram is regarded as a general optical system imaging, and modeling and optimization of EPISM method are proposed from two different aspects of angular spectrum and spatial domain. In the analysis of angle spectrum theory, the exit pupil function model is simplified firstly and the optical transfer function (OTF) with defocusing aberrations was established. In spatial domain analysis, the modulation characteristics of the hogel based holographic stereogram is constructed and validated while a diffraction-limited imaging model of the hogel based holographic stereogram is established, and the effective resolvable size of the reconstructed image point is simulated. The theories show that there is an optimal hogel size existed for the certain depth of scene. Optical experiments demonstrate the validity of our analysis, and the optimized parameters of hogel sizes can improve the imaging quality of full parallax holographic stereogram effectively.

Conventionally, a digital micromirror device (DMD) can only perform binary amplitude modulation of a light field. Simultaneous amplitude and phase modulation with a DMD is achieved by our proposed error diffusion scheme with a 4f double-lens setup for the first time. The DMD pixels are encoded by adaptive global optimization of binarization errors. In holographic projection, the object image can be optically reconstructed from a complex-amplitude hologram with this scheme. Experimental results show that our proposed error diffusion scheme significantly outperforms the previous superpixel scheme in terms of the image quality and light efficiency of holographic reconstruction results.

A simple yet effective method to realize holographic three-dimensional (3D) display by shifted Fraunhofer diffraction has been presented in this paper. After a 3D object is divided into a set of layers in axial direction, these layers are calculated into corresponding sub-holograms by Fraunhofer diffraction. The hologram uploaded on SLM consists of sub-holograms in a tiling approach. Both simulations and experiments are carried out to verify the feasibility of shifted Fraunhofer diffraction. Detailed analysis of computational cost has also been carried out, and the comparison between shifted Fresnel diffraction and shifted Fraunhofer diffraction in the proposed method has been analyzed. The experimental results demonstrate that our method can reconstruct multi-plane 3D object with continuous depth map and the process of 3D modeling is simple, that is the computational complexity is accordingly reduced.

We present a speckle reduction method to generate phase holograms with high-quality optical reconstruction based on optimized phase modulation. An initial phase with continuous and band-limited spectrum is utilized to iteratively optimize the phase modulation in the image plane. The optimized phase is used to modulate the object wave field, and the phase hologram is then calculated from the modulated object wave field. Phase distribution of the reconstructed image with our method is smoothly distributed and contains less phase singularities, which helps to reduce speckle noise in optical reconstruction. The proposed method can improve the reconstruction quality effectively, and eliminate the speckle noise induced by the random diffuse phase.

Illumination properties in imaging system have profound influence on the imaging characteristics that is ultimately observed. Structured illumination has been applied widely to three-dimensional microscopic imaging for obtaining super-resolution and sectional imaging. It is obvious that optimized and adaptive structured illumination results in expected image. Three-dimensional structured illumination can be produced by interference of multi-beam which is diffracted from a certain grating. Focusing on structured-light formed by multi-beam interference，the effect of phase grating modulation parameters on the properties of structured-light pattern are investigated in this work. Both simulated and experimental results show that the phase grating has higher diffraction efficiency and the phase modulation parameter of the sinusoidal phase grating has direct impact on the distribution of the structured light pattern. When the phase modulation parameter is optimized, the maximum modulation of structured-light pattern in three-dimension is obtained. Then we simulated the imaging of Fresnel incoherent correlation holography with optimized 3D structured illumination, and presented the improved reconstruction images.

We present a novel non-hogel-based computer generated hologram (CGH) technique which synthesizes complex field of 3D objects from its light field data, i.e. a number of views from different observation directions. Unlike conventional techniques, the proposed non-hogel-based CGH performs the global processing of the light field at each hologram pixel, making it free from spatio-angular resolution tradeoff, and enabling the generation of continuous parabolic wavefront for each object point without requiring associated depth map. We also present two efficient calculation techniques, i.e. the angular-frequency-slice-based processing and the hologram tiling that mitigate the computational load increased by the global processing of the non-hogel-based CGH.

Computation of the wave propagation from the 3D scene to the hologram plane is the fundamental basis for synthesizing 3D computer-generated holograms (CGHs). Computational accuracy and efficiency are directly related to the wave propagation model and sampling strategy used in the diffraction calculation. In this study, wave propagation procedures in different CGH algorithms are comprehensively analyzed in frequency domain, which illustrates the reconstruction properties of different algorithms. Further, a generalized frequency sampling strategy is introduced in calculating wave propagation with high computational efficiency and flexibility. Numerical simulations and optical experiments are conducted to illustrate the performances of the CGH algorithms.

A volumetric display generates three-dimensional (3D) graphics consisting of voxels in real space. It is a promising scheme of the volumetric displays to draw the voxels by 3D scanning of laser focusing points. The laser drawing method supports a wide viewing angle because these is no physical wiring between drawing space and the graphics forming system. The graphics size was ~ 1 cm³ in our previous research. In order to enlarge the volumetric bubble displays, the scan range should be increase with an objective lens with a long focal length. However, the increase gives an increase of the focusing diameter that requires an increase of the excitation energy. It is demonstrated that the use of gold nanoparticles was to decrease the excitation energy of the microbubbles.

Compared with other phase-only hologram generation approach, the bidirectional error diffusion algorithm eliminates the need for random phase and iteration, which significantly shortens the calculation time and improves the reconstructed image quality by reducing the influence of speckle noise. The basic concept of error diffusion method is compensating for the effect of removing amplitude information by diffusing the errors to their neighborhood unprocessed pixels. Based on this method, an optimization algorithm for phase-only hologram generation is proposed. The amplitudes of the errors used for diffusion are optimized by introducing a changeable coefficient for each different hologram. The simulation results show that the reconstructed image quality with the proposed optimization algorithm can be increased by up to 4 dB. Smoother amplitude information on the hologram plane can be obtained, thus less information is lost in the phase-only hologram generation process.

Reliable phase-only spatial light modulators (SLMs) are in demand for accurate phase modulation. However, the nonlinear optical response of liquid crystals and the limited manufacturing process can lead to the spatial nonuniformity of the phase modulation of the SLM. The transfer from the grayscale to the modulated phase can be different from the lookup table (LUT) shown in the SLM manual. The SLM should be measured for calibration. We propose a calibration method based on digital holography to calibrate the spatial nonuniformity of phase modulation of the SLM. Using a self-generated grating, the SLM involved system is converted to the calibration system based on the principle of digital holography. The in-situ strategy for low cost and efficient calibration was demonstrated with optical experiments using a 4K (3840 × 2160 pixels) phase-only SLM. The spatial nonuniformity was calibrated to decrease by more than 75% using only a beam splitter and an imaging sensor.

We propose a novel method for generating axial cosine structured light by using a phase-only spatial light modulator. The computer generates double concentric annular slits with different radii, and prism phase is applied on the slits so that the light beam incident on the slits is inclined away from the optical axis. The Bessel beams with different axial wave vectors generated by different annular beams, and the axial cosine structured light can be obtained from the interference between two Bessel beams. The period and phase of the axial cosine structured light can be adjusted by adjusting the radius and initial phase difference of the double concentric annular beam. We have proved theoretically and experimentally that this method can effectively generate axial cosine structured light.

In order to improve the effect, clarity and resolution of anti-counterfeiting, this paper proposes a method of reflection volume holographic three-dimensional (3D) anti-counterfeiting. This method adopts reflection volume holographic interference recording of 3D object to achieve 3D anti-counterfeiting. The principle of reflection volume holography was analyzed by using Kogelnik’s coupled wave theory. A reflection volume holographic anti-counterfeiting recording optical path based on a monochromatic laser was constructed. Photopolymer is used as the volume holographic recording material, and a metal school badge is used as the object. Experimental results show that the reflection holographic gratings can record and reproduce 3D object, and the 3D shape of the reproduced image is consistent with the object, which improves the effect of anti-counterfeiting.

Based on a complete system of boundary conditions for an electromagnetic field incident on a periodic structure, an algorithm is presented that allows you to convert such a system, leaving only the unknown amplitudes of the transmitted diffraction orders. The method underlying the algorithm belongs to the family of Fourier-space methods so devices and fields are represented as a sum of spatial harmonics. It is shown that the results of calculating the diffraction efficiency obtained using this approach completely coincide with the results obtained in the framework of the enhanced transmittance matrix approach and the scattering matrix approach. The dependences of diffraction efficiency on the wavelength and angle of incidence of the microstructure obtained by this method are presented. These results are consistent with the conclusions made in earlier studies, based on a different approach in the framework of a rigorous coupled-wave analysis.

To obtain high efficiency and high bandwidth grating based on large dispersion, we propose a 2-layer transmission grating with a high-line-density in this paper. A unitary fused-silica grating and a 2- layer grating combined with high and low refractive index dielectric material are designed respectively and their performance are compared briefly. The groove density of the grating is 1624 line/mm. By optimizing the grating parameters, the -1st diffraction efficiencies of the 2-layer transmission grating are both greater than 80% for TE and TM polarized incident lights in a wavelength range from 850nm to 1050nm and it can reach an efficiency of more than 97% for both polarizations at a central wavelength of 900nm when the light is incident from the front of grating. Moreover, we found that when the incident mode is in backside incidence mode, i.e. the light is incident from the back of grating, the -1st diffraction efficiency can reach to the maximum value of 97.9%.

Grating displacement measurement technology has been widely used in the field of position detection technology. In order to accurately measure the linear displacement of an object, a contactless displacement measurement technique is proposed. The single grating displacement sensing structure is adopted, and the interference fringes are collected by the linear array CCD camera driven by FPGA (field programmable gate array). The collected grating fringe signals are denoised, counted and subdivided based on DSP (digital signal processor). In this method, the subsequent circuit is simplified since the subdivision and digitization are completed with image capture by CCD simultaneously and the automatic real-time measurement of the target to be measured is realized. At the same time, the precision of the system is analyzed deeply.

As an advanced imaging technique, the polarization imaging has attracted more and more interests and many applications have been developed in the fields, such as biomedical diagnostics, target identification and remote sensing due to its unique ability to detect the polarization information of objects. On the other hand, the grating with its periodic spatial structure has been used widely in various imaging systems including but not limited to holographic imaging, Talbot effect of self-imaging, and imaging spectrometer. Furthermore, a sinusoidal amplitude grating is of considerable interest in image analysis and optical system characterization. Although many techniques with applications of the gratings have been developed in the last decades, few investigations have been made to the sinusoidal amplitude grating in a polarization imaging system with arbitrary illumination condition of polarization and coherence. In this paper, the polarization imaging of a sinusoidal amplitude object illuminated with a partially polarized and partially coherent light is investigated. With the help of the unified theory of polarization and coherence, we have extended the use of sinusoidal trace analysis in the evaluation of optical system performance and presented theoretical analysis on the Stokes images of a sinusoidal amplitude grating.

Digital holography enables the digitization processing of holograms. The resolution of the reconstructed image is greatly limited by the pixelated imaging detectors. This work investigates the effect of the initial hologram size on the imaging point spread function and introduces a bicubic interpolation and extrapolation iterative (BIPEPI) method. It circumvented the recording limitation in a certain extent to obtain more wave field information beyond the experimental recording area. The bicubic interpolation (BIP) method increases the pixel density inside the hologram to enhance the low-frequency terms of the object. With extrapolation iterative (EPI) method, more high order fringes around the experimental hologram are generated to enhance the high-frequency terms of the object. This method can improve the point spread function of small size detector to effectively increase the reconstructed resolution.

The large field of view projection system based on the principle of diffraction has a simple optical system, but it often consumes a lot of time when calculating the hologram using the traditional iterative algorithm, which limits the application range of the system. In this paper, we use deep learning to accelerate the calculation of holograms, and experiment results proves that the holograms calculated by U-net have good performance.

Diffractive optics are promising for use in interferometry as a Transmission Sphere (TS) due to the fact that it is simpler and cheaper, since it consists of one component. However, in the manufacture and use of Diffractive TS (DTS) with an aperture up to f/1, many problems arise that are not specific for classical TS. One of these problems is the effects of polarization, which can affect the interferogram. These negative effects can occur when diffractive TS has a period close to the interferometer wavelength. This work is devoted to computer simulation of such effects and development of technique for their partial compensation. To avoid the harmful effects of laser beam depolarization and to decrease the two-pass transmittance of a typical DTS at its margins, we decompose the local linear polarization into the radial and azimuthal components and evaluate separately the forward and backward transmittance of each polarization component for the case with a spatially variable prescribed local duty cycle.

An optimization algorithm is developed to extend the unambiguous range of DWDH, which is suitable for imaging living onion epidermal cells, and meanwhile to reduce the noise. In the experiments, the holograms with two wavelengths can be acquired in a single shot recording by using off-axis dual-wavelength digital holography, resulting to obtain their two sets of spatial spectrum via Fourier transform for these two holograms. The denoised unwrapping phase image of sample is straightforward reconstructed with the optimization algorithm, instead of increasing the noise due to longer synthetic wavelength. As a result, the unwrapped phase images of onion epidermal cells are achieved.

In this paper, an off-axis digital holography multi-frame image super-resolution reconstruction method is presented. Each low-resolution hologram will have small displacement in different directions. The obtained low-resolution holograms are processed iteratively with the super-resolution algorithm to obtain the super-resolution hologram, and then the amplitude image is reconstructed from the super-resolution hologram. The imaging results show that the resolution of the reconstructed image after super-resolution processing is obviously improved, because of increase of high-frequency information in the high-resolution hologram.

A band-limited double-phase hologram (DPH) is proposed based on the single-pixel on-axis double-phase technique. The proposed band-limited DPH introduces a band-limited function into the propagation calculation and previously remove high-noise frequency components. The reconstruction is equipped with a higher spatial resolution and an expanded SBP by enabling the enlargement of the aperture in 4-f system.

The algorithm for estimating the linewidth for metal oxide grating embedded in the grooves of metal grating by analyzing diffractometric measurements in transmitted and reflected light are considered. To calculate the diffraction efficiency under of rigorous electromagnetic theory, the developed algorithm uses the functions of the GD-Calc toolkit. The estimation of the linewidth from the diffraction efficiency analysis for 1μm period of the grating formed on a Ti film has demonstrated discrepancy near 5% with result obtained from analysis microimages.

A completely “dry” one-step method for the formation of reflective phase diffractive optical elements (DOE) using direct laser writing on thin Zr film without subsequent liquid or plasma treatment has been demonstrated. The method is based on effect of nanostructure formation during the thermochemical oxidation of the zirconium film deposited on a fused silica substrate. Direct laser writing of diffractive structures is performed by scanning a laser beam with a wavelength of 405- 532 nm, focused into a spot with a diameter of 400-700 nm. When line-by-line scanning with a step of 200-500 nm, the formation of nanogratings from tracks with a width of 70-100 nm and with a period equal to the scanning step was observed. It was experimentally established that lines in the form of cracks or deformations arise along the contour of the spatial distribution of temperature induced by the laser beam heating. Cracks or deformations occur under the influence of thermomechanical stresses at the boundary between the metal film and the oxide line, the thickness of which increases sharply during the oxidation of the metal. The formed nanogratings significantly change the optical properties of the film surface. Measurements by a white light interferometer show the presence of a relief with a depth of -200 to +500 nm, although when oxidizing a 100-nm thick Zr film, the increase in thickness cannot exceed 50-60 nm. Binary diffractive structures with a period of 0.9 - 10 μm, the diffraction efficiency of which exceeded 30%, were made by the new method. The one-step method can be useful for the manufacture of computer-generated holograms used in testing of aspherical surfaces.

To explore the effect of the incident polarization on achieving polarization-controllable multifocal arrays (MFAs), the polarization-controllable MFAs generated by radially polarized (RP) and azimuthally polarized (AP) beams are compared in this work. Four phase filters for the numerical aperture (NA) of 0.80, 0.85, 0.90 and 0.95 are respectively designed to generate the polarization-controllable MFAs under the illumination of RP and AP beams. The intensity comparison demonstrates that the polarization-controllable MFAs generated by AP beams have the higher uniformity, smaller focal spots and more stable intensity distributions for the same NA. The polarization comparison demonstrates that the polarization properties of the polarization-controllable MFAs generated by AP beams are more consistent with the desired target. Therefore, the AP incident beam is the better choice to realize a polarization-controllable MFA by a phase filter.

The grating diffraction intensity distribution law is an important link in both optics and college physics courses. Grating diffraction experiments are also very important in physics experiments. However, the gratings involved in optics and college physics experiments are all Equal period, the distribution of grating diffraction intensity in this has been researched quite mature. However, in some engineering fields, the intensity distribution law of a non-equal period grating diffraction is often concerned. In this paper, based on Kirchhoff diffraction theory, Fraunhofer diffraction conditions are applied, and the Huygens-Fresnel principle Starting from, it is feasible to apply the Fourier transform method to deal with the distribution law of light intensity of non-constant period gratings. Then it is further explained that there is a certain regularity of the light intensity distribution law and the characteristics of the grating after diffraction by the non-equal period grating.

Phase extraction and applications of the speckle vortex field with spiral wavefront and stable core structures of phase singularities has become an important research content in the field of optical measurement. Phase singularities in the speckle field constitute singular skeleton. We use an experimental system to measure the deformation displacement based on the singular skeleton. In the experiment, a liquid crystal spatial light modulator (LC–SLM) is used to generate speckle field, and the output speckle image is captured by the CCD camera. By processing the speckle pattern, the singular skeleton of the speckle field is depicted. Based on the singular skeleton, the deformation translational displacement of the test sample is obtained. The experimental results show that high-resolution optical measurement methods can be developed based on the singular skeleton of the speckle field.

Phase unwrapping is a classical signal processing problem, which refers to the recovery of the original phase value from the wrapped phase. Two dimensional phase unwrapping is widely used in optical measurement technology, such as digital holographic interferometry, fringe projection profilometry, synthetic aperture radar and many other applications. In this paper, a phase unwrapping method with the convolution neural network is proposed, and the feasibility is analyzed by numerical simulation. The convolution neural networks with different parameters are set up, and the phase screens used for the training set and testing set of convolution neural network are simulated with MATLAB software. The numerical simulation results show that the four convolution neural network models can be used for phase unwrapping, but the parameters have a significant impact on its accuracy.