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Due to physical limitation in resolution of display device, it is usually very difficult to achieve a high spatial resolution and a high angular resolution simultaneously for a three-dimensional (3D) light field display. Here, a computational super-resolution full-parallax 3D light field display is demonstrated, which can achieve both high spatial resolution and angular resolution. The proposed display consists of a specially designed backlight unit with controlled scattering angle, two cascadedly arranged LCDs with a resolution of 3840 × 2160, an aberration-suppressed compound lens array, and a holographic functional screen. The optical image formation processing of the display is analyzed and modeled as a whole process, and the superresolution light field synthesis method is presented. By co-designing the optical elements with computation processing, our proposed display architecture can improve the spatial resolution and angular resolution with a factor of 2× in both horizontal and vertical directions, comparing with these of the conventional light field display with single LCD and standard lens array. Finally, a super-resolution full-parallax 3D light field display with a designed spatial resolution of about 640 × 360 in a display area of 21.5 inches and an angular resolution of 166 × 166 in a viewing angle of 45 × 45 degrees is constructed, and an excellent 3D visual experience with improved image quality can be perceived.

Stereo depth estimation is an efficient method to perceive three-dimensional structures in real scenes. In this paper, we propose a novel self-supervised method, to the best of our knowledge, to extract depth information by learning bi-directional pixel movement with convolutional neural networks (CNNs). Given left and right views, we use CNNs to learn the task of middle-view synthesis for perceiving bi-directional pixel movement from left-right views to the middle view. The information of pixel movement will be stored in the features after CNNs are trained. Then we use several convolutional layers to extract the information of pixel movement for estimating a depth map of the given scene. Experiments show that our proposed method can significantly provide a high-quality depth map using only a color image as a supervisory signal.

In this paper, a polarization-insensitive reverse-ridge AlGaAs waveguide is designed for the supercontinuum generation. In the considered wavelength range from 3.4 to 8 μ m, the dispersion profiles, nonlinear coefficients, and effective mode field areas for the quasi-TE and quasi-TM modes coincide well. The simulation results show that when pump pulse with wavelength of 4.2 μ m, peak power of 4.8 kW, and width of 90 fs is launched into the anomalous dispersion region of the quasi-TE and quasi-TM modes of the 3.4-mm-long waveguide, the two generated SCs overlap well. For the quasi-TE and quasi-TM modes, the SCs generated extend from 2.17 to 8.53 μ m and 2.23 to 8.61 μ m, respectively, spanning more than 1.95 octaves. The proposed reverse-ridge AlGaAs waveguide structure is expected to provide a possible solution for alleviating the undesired polarization effect related to the nonlinear dynamics.

Reflection and refraction images are treated as the texture of the object in computer graphics, which brings wrong depth information when focusing on the object in holographic display. In this paper, a method of ray tracing rendering with complete depth information for computer-generated hologram(CGH) is proposed. Correct depths of reflection and refraction images are calculated, and layer-based method is used to generate CGH. In experiment result, our method truthfully reconstructs the complete depth information of complex scene. Reflection or refraction images and its corresponding media surfaces can be focused on correct depth. All layer data is computed in a single ray tracing procedure, and the generation speed of 1024×1024 CGH for 3D scene divided into 10 layers is 100fps.

Three-dimensional (3D) light-field displays (LFDs) suffer from a narrow viewing angle, limited depth range, and low spatial information capacity, which limit their diversified application. Because the number of pixels used to construct 3D spatial information is limited, increasing the viewing angle reduces the viewpoint density, which degrades the 3D performance. A solution based on a holographic functional screen (HFS) and a ladder-compound lenticular lens unit (LC-LLU) is proposed to increase the viewing angle while optimizing the viewpoint utilization. The LC-LLU and HFS are used to create 160 non-uniformly distributed viewpoints with low crosstalk, which increases the viewpoint density in the middle viewing zone and provides clear monocular depth cues. The corresponding coding method is presented as well. The optimized compound lenticular lens array can balance between suppressing aberration and improving displayed quality. The simulations and experiments show that the proposed 3D LFD can present natural 3D images with the right perception and occlusion relationship within a 65° viewing angle.

For a floating three-dimensional (3D) display system using a prism type retroreflector, non-retroreflected light and a blurred 3D image source are two key causes of the deterioration in image quality. In the present study, ray tracing is used to analyze the light distribution of a retroreflector at different incident angles. Based on this analysis, a telecentric retroreflector (TCRR) is proposed to suppress non-retroreflected light without sacrificing the viewing angle. A contrast transfer function (CTF) is used to evaluate the optical performance of the TCRR. To improve the 3D image source, the relationship between the root mean square (RMS) of the voxels and the 3D image quality is discussed, and an aspheric lens array is designed to reduce aberrations. Computational simulation results reveal that the structural similarity (SSIM) of the 3D image source increased to 0.9415. An experimental prototype system combining the TCRR and optimized 3D image source is then built. Experimental analysis demonstrates that the proposed method suppresses non-retroreflected light and improves the 3D image source. In particular, a clear floating 3D image with a floating distance of 70 mm and a viewing angle of 50° can be achieved

In this paper, a reverse-strip AlGaAs waveguide with three zero-dispersion wavelengths (ZDWs) is designed. The corresponding three ZDWs are located at 3.74, 6.56, and 8.89 µm. The nonlinearity coefficient of the proposed reverse-strip AlGaAs waveguide is calculated as 2.09 W − 1 m − 1 at wavelength 4.9 µm. The effects of pump pulse parameters, waveguide length, and noise coefficient on the nonlinear dynamics of supercontinuum (SC) generation are investigated. When the hyperbolic secant pump pulse with a wavelength of 4.9 µm, peak power of 900 W, and duration of 100 fs is launched into the proposed waveguide and propagated after a 3 mm length, highly coherent and multi-octave mid-infrared (MIR) SC spanning from 2.2 to 14.5 µm (more than 2.7 octaves, at − 40 d B level) is generated. Finally, a possible fabrication process of the reverse-strip AlGaAs waveguide is introduced. Our research results have important applications in MIR photonics, MIR spectroscopy, optical precision measurement, and more.

In this paper, a V-shape photonic crystal fiber (PCF) polarization filter based on surface plasmon resonance (SPR) effect is proposed. With the full vector finite element method, the V-shape photonic crystal fiber polarization filter is designed, and the coupling characteristics between the core mode and surface plasmon polariton mode are analyzed. The simulation results show that the fiber parameters have significant effects on the shift and strength of the SPR wavelength. Moreover, the losses of the core modes along the Y and X polarization directions are 68904 dB/m and 858 dB/m at the SPR wavelength of 1550 nm, respectively. Finally, the extinction ratio and error-tolerant rate of extinction ratio are also analyzed. The proposed V-shape PCF polarization filter can achieve good filtering effect in the communication band and is easy to integrate with existing optical fiber communication and sensing systems.

In this paper, we numerically investigate the generation of parabolic pulse (PP) in a silicon waveguide taper with simultaneous variations of the group-velocity dispersion and nonlinearity along the propagation direction. The design of such a waveguide taper is based on the condition of self-similar propagation of the PP. When Gaussian, hyperbolic secant, and super-Gaussian pulses are propagated inside the waveguide taper designed, the evolution processes under the ideal condition are analyzed. Then the PP generation from Gaussian input is shown when higher-order dispersion, higher-order nonlinearity, linear loss, two-photon absorption, free-carrier absorption, and free-carrier dispersion are taken into account. Moreover, the influences of the initial chirp, pulse width, peak power, and waveguide length on the PP generation are further discussed. It is demonstrated that high-quality PP can be obtained with a mismatch parameter as low as 1 . 3 × 1 0 − 3 , in the designed silicon waveguide taper.

A lightweight, compact and wide field of view (FOV) reflective type head-mounted display (HMD) system with off-axis three-mirror (OTM) imaging technology is proposed. The surfaces of all the mirrors in this system are freeform type, which possess excellent aberration correction properties even with fewer optical elements for a compact design. The design and optimization process of the proposed wide FOV OTM-HMD system are described in detail. Our HMD system has a diagonal FOV of 40 degrees and the maximum distortion of the system is less than 5%. The modulation transfer function (MTF) value was found to be larger than 0.1 at the spatial frequency of 60 cycles/mm. A binocular prototype (total size: 160 mm × 56 mm × 36 mm) meeting the human ergonomic requirements was built using the proposed design and the optical performance of the prototype was tested. While being compact, lightweight and cost-efficient, the optical performance of our OTM-HMD system is comparable to that of other previously reported HMD systems.

An improved integral imaging system with large viewing angle using the micro-lens array mask (MLAM) is demonstrated. Currently, the limitation of viewing angle is one of primary defects of the conventional integral imaging (InIm). Here, a novel MLAM is designed and fabricated to eliminate this limitation, and a mapping relationship of coding is presented to guarantee the perceived 3D image with correct occlusion relation. The viewing angle of the proposed InIm-improved system are significantly improved without decreasing the spatial display resolution of the displayed 3D images. In the experiment, a demonstrated prototype system using the MLAM and a 23.6-in. liquid crystal display (LCD) panel with the resolution of 3840 × 2160 is realized with 45° viewing angle, which can provide a natural 3D visual effect with high quality.

With the increasing application of light field, especially in the light field display field (LFD), more and more light field data are required. However, there are some disadvantages for current light field acquisition methods, such as high hardware cost, low spatial resolution and other defects. A novel light field acquisition method using external mask and compressive sensing theory is presented. Different from the conventional methods with the camera array or the light field camera based on the micro-lens array, an external mask is pasted on the large aperture lens of an ordinary camera, and the 3D scene is captured at several typical positions. The compressive sensing theory is introduced to recover the original light field data ( 5 × 5 ) even though the photos captured by camera is vignette and with a limited field-of-view (F.O.V) of the lens. Simulation is carried to confirm our method with a good SSIM. The acquired light field data with our method is demonstrated with a light field display, and the validity of the proposed method is proved.

A layered rendering method for generating computer-generated hologram (CGH) of 3D objects based on view volume transformation is presented. The shape distortion and the size deviation of the 3D reconstructed image existing in conventional layer-based methods are avoided, and the reconstructed 3D image can preserve the real size of the original model with high quality. Real-time interaction with the digitally reconstructed holographic image with clear depth cues is experimentally demonstrated.

In this paper, we numerically demonstrate efficient spectral compression (SPC) of wavelength-shifting soliton in a chalcogenide strip waveguide. It is found that the profiles of group-velocity dispersion (GVD) and Kerr nonlinearity play key roles in determining SPC. After calculating the dispersion of Kerr nonlinearity and Raman spectrum for three kinds of chalcogenide materials, Ge11.5As24Se64.5 is chosen as the material for designing the chalcogenide strip waveguide (CSW). The geometric parameters of CSW are optimized to obtain the desired GVD and Kerr nonlinearity. Simulation results show that in the designed CSW, an input spectrum width of 52.04 nm can be compressed to 7.23 nm along with wavelength shift of 17 nm when the input peak power is 25 W. With the input peak power increasing to 75 W, the SPC is slightly weakened, but wavelength shift can be up to 190 nm. The proposed CSW is applied to integrated all-optical quantization and an effective quantization number of 3.66-bit is achieved. It is expected that our research results can find important applications in on-chip integrated spectroscopy, all-optical signal processing, etc.

Lens aberrations degrade the image quality and limit the viewing angle of light-field displays. In the present study, an approach to aberration reduction based on a pre-correction convolutional neural network (CNN) is demonstrated. The pre-correction CNN is employed to transform the elemental image array (EIA) generated by a virtual camera array into a pre-corrected EIA (PEIA). The pre-correction CNN is built and trained based on the aberrations of the lens array. The resulting PEIA, rather than the EIA, is presented on the liquid crystal display. Via the optical transformation of the lens array, higher quality 3D images are obtained. The validity of the proposed method is confirmed through simulations and optical experiments. A 70-degree viewing angle light field display with the improved image quality is demonstrated.

A polarization beam splitter (PBS) based on dual-core photonic crystal fiber (DC-PCF) with three layers of elliptical air holes is proposed. The full-vector finite element method is used to investigate the coupling and propagation characteristics of the PBS, and the three-dimensional beam propagation method is used to demonstrate the evolutions of the x-pol and y-pol light fields in cores A and B of the DC-PCF. In this design, the elliptical air holes are introduced to enhance the birefringence of the DC-PCF. The simulation results show that, with the proposed PBS, the complete beam splitting can be achieved at wavelength 1.55 μm when the fiber length is 254 μm. Moreover, when the extinction ratio is less than −20 dB, the bandwidth of the PBS can be up to 48 nm, covering the whole C-band. It is believed that the proposed PBS will be a promising candidate in laser and sensor systems.

Despite the light field display with many advantages is considered as one of the most potential three-dimensional display technologies, the limited depth range is common drawback which restricts its applications. Small depth of focus (DOF) caused by diffraction is one of the reasons those limit the display depth range. Here, the proposed method extends the display depth range by enlarging DOF of the lens. In order to verify the feasibility of the method, a 32-inch three-dimensional light-field display system based on the controlling-light structure in cross arrangement and holographic functional screen (HFS) is demonstrated. Two extended DOFs are superposed to form the extended depth due to the controlling-light structure in cross arrangement combined by lenslet array and aperture array. The function of HFS is to modulate and rebuild the light field distribution so as to eliminate the gaps between the adjacent lenslets and increase the fill factor of the controlling-light structure. In terms of contrast experiments, the depth range of the improved display system is extended effectively, which is extended from 6 cm to 13 cm on the premise of the 40° horizontal and vertical viewing angle and acceptable resolution.

Three-dimensional (3D) light field display can reconstruct vector of light field of 3D scene eliminating convergence-adjustment conflict (CAC) with full parallax and nature color cues, however it suffers from its limited viewing-angle, the mediocre display resolution, an insufficient gross of viewing perspectives and the complex setup. Here, a large horizontal viewing-angle 3D light field display with horizontal viewing zone of 70° and vertical viewing zone of 35° without resolution reduction based on liquid crystal barrier (LC-Barrier) and time-division-multiplexing (TDM) is presented. The proposed 3D light field display consists of a holographic functional screen (HFS), a lens array (LA), an LC-Barrier and a 28-inch LCD with resolution of 3840 × 2160. By analyzing the corresponding relationships of rays from elemental image array (EIA), a series of pixel-mapping equations are derived. Moreover, the issue that horizontal resolution will decrease as the horizontal viewing-angle doubles can be addressed by enhancing the resolution utilizing TDM. The fill factor is introduced to evaluate the imaging effect. Experimental results demonstrate that the large horizontal viewing-angle 3D light field display based on LC-Barrier and TDM can present actual 3D stereoscope images with correct occlusion and perception.

With hollow-core negative curvature fiber, a refractive index (RI) sensor based on surface plasmon resonance effect is proposed. The average sensitivity can be up to -7024 nm/RIU in the RI range from 1.29 to 1.39.

In this paper, a T-type germanium (Ge) waveguide with an all-normal dispersion profile is designed for mid-infrared (MIR) supercontinuum (SC) and frequency comb generations. The nonlinearity coefficient of the designed waveguide is calculated as 30.48 W-1·m-1 at the initial pump wavelength of 3.0 µm. Moreover, the group-velocity dispersion is kept low and flat in the considered wavelength range. Simulation results show that with the designed waveguide, the highly coherent and octave-spanning MIR SC can be generated in the wavelength range from 1.85 to 9.98 µm (more than 2.4 octaves) when the pump pulse with wavelength of 3.0 µm, peak power of 900 W, and duration of 120 fs is launched into the 5 mm long waveguide. When the pulse train including 50 pulses at a repetition rate of 100 MHz is used as the pump source, the SC-based frequency comb is obtained.

In this paper, a novel silicon photonic crystal fiber (Si-PCF) polarization filter based on surface plasmon resonance effect is proposed for the first time. With the full-vector finite-element method, the mode coupling characteristics of the Si-PCF with the gold-coated film between the core mode and surface plasmon polariton mode are investigated, and the confinement losses are analyzed. The confinement losses of the Y-polarized core mode at the three resonant wavelengths 2.84, 3.29, and 4. 53 μ m are 9235.9, 27097.5, and 97818.3 dB/m, respectively. The extinction ratio reaches -391 dB and the insertion loss is less than 1 dB when the Si-PCF length is 4 mm, along with the filter bandwidth of 2. 75 μ m . Moreover, by modifying the fiber structure parameters, the filter bandwidth of the proposed three kinds of Si-PCF polarization filters can cover 2.75 to 7. 80 μ m . It is believed that the proposed Si-PCF polarization filter has important applications in the mid-infrared laser and optical communication systems.

A method for adjusting the differential order of a silicon-based waveguide grating differentiator by inputting light, which is through two-photon absorption and free carrier absorption effects, is proposed. The simulation results are demonstrated.

We propose and demonstrate a directional bend sensing based on Mach-Zehnder interferometer in a high birefringence dual-core photonic crystal fiber. Its curvature sensitivity is up to 4.24 nm/m–1 within the curvature range of 2.19-3.99 m–1.

A holographic visualization of volume data based on adjustable ray to optical-wave conversion is presented. Computer-generated holograms are generated by emitting multiple rays to sample the volumetric field. Equal interval sampling, object light wave adjustment, and information composition are sequentially performed during the march of rays. The program is accelerated in parallel to reduce the total time, and the reconstructions are dynamically adjusted to express different parts of an object. Optical experiments verify that the proposed method can holographically reconstruct the surface and interior information of objects.

The pseudoscopic image, which is also called depth reverse, is an inherent problem of integral imaging display. Here a high efficient and precise pseudoscopic-to-orthoscopic conversion method is presented to address this issue. In addition, off-axis pickup method is used for capturing the perspective images of 3D scene. With this method, there is no redundant information, which saves the storage space and increases the utilization ratio of the captured information of 3D scene. The pixel mapping process is a point-to-point procedure, which is more precise. Experimental results shows that the display quality of the reconstructed 3D images is improved, and the analysis verifies the feasibility of the proposed method.

Holograms can reconstruct the complete optical wave field of a three-dimensional (3D) scene. However, generating traditional computer-generated holograms (CGHs) requires significant computing time. Here, a CGH method is presented based on backward ray tracing and wavefront recording planes (WRPs). Ray tracing is able to render more complex and photorealistic images for different illuminations and circumstances. Rays are parallelly launched and traced to obtain ray-object intersections, and then the complex wave field of the effective pixels in the WRP is determined. A CGH is generated by the diffracted calculation from the WRP to the hologram plane using fast Fourier transform (FFT) and inverse FFT algorithms. Experimental results demonstrate the effectiveness of the proposed method. Compared with traditional CGHs, the rate of CGH generation and optical reconstruction improves to 35.6 frames per second, achieving the real-time rendering and interactivity.

In this paper, a chalcogenide-based ridge waveguide with a suspended structure on the substrate of Si 3 N 4 , is designed, which is demonstrated to have low and flat dispersion profiles. Simulation results show that when the higher-order nonlinear effects and linear loss are considered, a broadband supercontinuum with high coherence ranging from 1.0 to 5. 6 μ m is obtained after a 3.1-mm long propagation when pumping wavelength 2. 65 μ m and peak power 450 W. Our proposed scheme provides a promising solution to realize broadband and highly coherent SC in mid-infrared region for nonlinear photonics and spectroscopy.

An improved integral imaging with large viewing angle based on two crossed lenticular lens combined arrays (LLCAs) is demonstrated. The limitation of the viewing angle of the perceived three-dimensional (3D) scene constructed by the conventional integral imaging (InIm) is one of the most primary drawbacks of the conventional InIm for its commercial application. Here, the LLCA is designed and fabricated to enlarge the viewing angle, and the perceived 3D scene with large viewing angle produced by the proposed improved-InIm with two crossed LLCAs is presented. In the experiment, an improved InIm with 44° viewing angle based on two crossed LLCAs and the 23.6-inch liquid crystal display (LCD) panel with the resolution of 3840 × 2160 is realized, which can provide natural 3D visual effect with high quality.

A floating aerial three-dimensional (3D) display based on the freeform-mirror and the improved integral imaging system is demonstrated. In the traditional integral imaging (II), the distortion originating from lens aberration warps elemental images and degrades the visual effect severely. To correct the distortion of the observed pixels and to improve the image quality, a directional diffuser screen (DDS) is introduced. However, the improved integral imaging system can hardly present realistic images with the large off-screen depth, which limits floating aerial visual experience. To display the 3D image in the free space, the off-axis reflection system with the freeform-mirror is designed. By combining the improved II and the designed freeform optical element, the floating aerial 3D image is presented.

The floating 3D display system based on Tessar array and directional diffuser screen is proposed. The directional diffuser screen can smoothen the gap of lens array and make the 3D image’s brightness continuous. The optical structure and aberration characteristics of the floating three-dimensional (3D) display system are analyzed. The simulation and experiment are carried out, which show that the 3D image quality becomes more and more deteriorative with the further distance of the image plane and the increasing viewing angle. To suppress the aberrations, the Tessar array is proposed according to the aberration characteristics of the floating 3D display system. A 3840 × 2160 liquid crystal display panel (LCD) with the size of 23.6 inches, a directional diffuser screen and a Tessar array are used to display the final 3D images. The aberrations are reduced and the definition is improved compared with that of the display with a single-lens array. The display depth of more than 20 cm and the viewing angle of more than 45° can be achieved.

A 54-inch horizontal-parallax only light-field display based on the light-emitting diode (LED) panel and the micro-pinhole unit array (MPUA) is demonstrated. Normally, the perceived 3D effect of the three-dimensional (3D) display with smooth motion parallax and abundant light-field information can be enhanced with increasing the density of viewpoints. However, the density of viewpoints is inversely proportional to the spatial display resolution for the conventional integral imaging. Here, a special MPUA is designed and fabricated, and the displayed 3D scene constructed by the proposed horizontal light-field display is presented. Compared with the conventional integral imaging, both the density of horizontal viewpoints and the spatial display resolution are significantly improved. In the experiment, A 54-inch horizontal light-field display with 42.8° viewing angle based on the LED panel with the resolution of 1280 × 720 and the MPUA is realized, which can provide natural 3D visual effect to observers with high quality.

Holographic displays can provide the complete optical wave field of a three-dimensional (3D) scene, including the depth perception. However, it often takes a long computation time to produce traditional computer-generated holograms (CGHs) without more complex and photorealistic rendering. The backward ray-tracing technique is able to render photorealistic high-quality images, which noticeably reduce the computation time achieved from the high-degree parallelism. Here, a high-efficiency photorealistic computer-generated hologram method is presented based on the ray-tracing technique. Rays are parallelly launched and traced under different illuminations and circumstances. Experimental results demonstrate the effectiveness of the proposed method. Compared with the traditional point cloud CGH, the computation time is decreased to 24 s to reconstruct a 3D object of 100 × 100 rays with continuous depth change.

Aberrations caused by optical lens refraction in a light-field display (LFD) are minimized based on real-time pre-rectification. A virtual optical lens with the high precision surface is developed the constructive solid geometry under minimum primitives to rectify the sampling rays, and the virtual lens exhibits the same response to different incident ray wavelengths as the real lens in the LFD optical domain. In addition, assembly misalignment is taken into consideration during the partitioning of the elemental image array so that all the elemental images and the covering lenses can be precisely aligned. After rectifying the sampling rays with the constructed virtual lens, the rays are launched in parallel in the GPU, and path tracing is conducted to shade the element image array. The proposed approach ensures the consistency of the integral photography and LFD processes, which minimize the distortion and increasing the depth of field for three-dimensional (3D) images. Experimental results verify the feasibility of our proposed method. The structural similarity index is improved by 0.1, and 3D images at different depths are correctly expressed. Only three primitives are introduced to the system as a whole, meaning that the extra computation has little impact on the rendering efficiency. Consequently, the real-time generation of 3D light-field images is possible.

In three-dimensional (3D) light-field displays, the quality of a reconstructed image degrades with increasing depth of field due to the pixel deviation effect. A fitting algorithm of dense-viewpoints is proposed to reduce the pixel deviation with high image quality. To analyze the pixel deviation effect, the human vision-based perspectives perceived from 3D light-field display system with the holographic functional screen are mathematically modeled. The optimized synthetic image is coded according to the mapping relationship from the display model and the optimal Gaussian distribution parameters achieved with the maximum likelihood estimation method. The effectivenesses of the proposed model and the optimization method are verified through simulations as well as optical experiments. A human vision-based high resolution 3D light-field display with 45-degree viewing angle and the large depth of field is achieved.

Three-Dimensional (3D) light-field display plays a vital role in realizing 3D display. However, the real-time high quality 3D light-field display is difficult, because super high-resolution 3D light field images are hard to be achieved in real-time. Although extensive research has been carried out on fast 3D light-field image generation, no single study exists to satisfy real-time 3D image generation and display with super high-resolution such as 7680×4320. To fulfill real-time 3D light-field display with super high-resolution, a two-stage 3D image generation method based on path tracing and image super-resolution (SR) is proposed, which takes less time to render 3D images than previous methods. In the first stage, path tracing is used to generate low-resolution 3D images with sparse views based on Monte-Carlo integration. In the second stage, a lite SR algorithm based on a generative adversarial network (GAN) is presented to up-sample the low-resolution 3D images to high-resolution 3D images of dense views with photo-realistic image quality. To implement the second stage efficiently and effectively, the elemental images (EIs) are super-resolved individually for better image quality and geometry accuracy, and a foreground selection scheme based on ray casting is developed to improve the rendering performance. Finally, the output EIs from CNN are used to recompose the high-resolution 3D images. Experimental results demonstrate that real-time 3D light-field display over 30fps at 8K resolution can be realized, while the structural similarity (SSIM) can be over 0.90. It is hoped that the proposed method will contribute to the field of real-time 3D light-field display.

Compared with traditional integral imaging systems, light-field displays (LFDs) based on a holographic functional screen (HFS) shows significant advantages in terms of the number of viewpoints, large viewing angle, and high viewing resolution. LFDs usually suffer from a limited depth range, and the reason majorly originates from the pixel deviation effect in the reconstruction process. Here, an analysis method for the depth of field (DOF) based on the pixel deviation effect observed on the HFS plane is presented. Simulation experiments are carried out to show that the percentage of pixel deviation is a more accurate measure to calculate the DOF. The feasibility of this method is verified in optical experiments.

Computer-generated multi-view (MV) image for the three-dimensional (3D) display with lenticular lens arrays based on the backward ray-tracing technique is presented. To overcome the limitations of the traditional ray-tracing technique, whose minimum operating unit is the pixel, the proposed method can be applied at the sub-pixel level. The quality of the generated 3D image is not reduced, in contrast to existing methods for converting 2D images to 3D. Compared to the previous each camera viewpoint independent rendering method, the backward ray-tracing technique directly renders the final MV image rather than all the single-viewpoint images. Accordingly, the total render time is substantially reduced. Experimental results show that our proposed method significantly increases the simplicity and efficiency of the rendering process, especially ensuring the resolution of the final MV 3D image. Experimental results for 3D display with the generated 32-viewpoint 3D images are presented.

A wide field of view (FOV) tabletop light field display (LFD) based on piece-wise tracking and off-axis pickup is presented to display the floating three-dimensional (3D) scene, which is 360°surrounding viewable. The demonstrated LFD is specially designed with an integral imaging display (IID) with 83 × 83 viewpoints and a full-parallax holographic functional screen (HFS). To improve the FOV, a piece-wise tracking based FOV enhancement method is proposed. The relationship between the viewing zone and the elemental images (EIs) is formulated. A ray-tracing based method using off-axis pickup instead of parallel pickup directly is adopted to render the 3D scene to EIs. Then the piece-wise tracking method of varying the viewing zone by placing the EIs according to the position of viewer is analyzed. The floating 3D scene with a FOV of 70° × 70°is experimentally demonstrated with a good 3D perception.

In this paper, a silicon concentric dual-microring resonator for refractive index sensing is designed. The influences of the mode effective index difference, extinction ratio (ER), and sensitivity on the homogeneous sensing of sucrose solutions are investigated by using 3-D finite-difference time-domain (FDTD) method. The geometry structures of the concentric dual-microring resonator are optimized to satisfy the desired sensing performance. Moreover, a refractive index sensor based on the designed concentric dual-microring resonator is proposed, which can realize the ER of 30 dB, sensitivity of 180 nm/refractive index units (RIU), and detection limit of 1.1×10 −5 RIU. It is believed that the proposed refractive index sensor can find important application in the refractive index sensing.

A multi-view content generation method for three-dimensional (3D) display without depth-reversed area is demonstrated. The viewing zone periodicity of an autostereoscopic display is utilized to eliminate the depth-reversal by adjusting the light field alignment in the 3D light field. The conditions that a multi-view sequence should satisfies to form a depth-reversal-free sequence are given and detailed processes for converting the multi-view sequence into a depth-reversal-free sequence are presented. Experimental results show that the depth-reversed area is well eliminated, and the smooth motion parallax can be achieved when the viewer moves in front of the display within a 60°viewing angle. The number of presented perspectives can be 8 times more than the viewpoint number of the autostereoscopic display with the help of viewing zones integration.

A typical integral imaging (InIm) display consists of the pickup process and the display process. In the InIm display process, the facet braiding phenomenon influences on the depth of field (DOF). Actually, the DOF of the InIm system not only depends on the the facet braiding in the display process, but also seriously depends on the pickup process. Only the pickuped object within the certain region can capture clear elemental images, and blurry elemental images could be attained outside the region. The region that can be recorded clear elemental images is called the pickup DOF of InIm, which influences on the total DOF of the InIm display. The pickup DOF calculation formula of InIm is presented, which is compared with the DOF caused by facet braiding. Experimental results agree with the theoretical analysis, which is benificial for designing the InIm display system.

In conclusion, simultaneous measurement of surrounding RI and temperature changes can be achieved by using two WGMs. The transmission responses of the WGM (1, 28) and WGM (0,36) with different Wgap indicate their different coupling status. The RI and temperature sensing performances by monitoring the resonance wavelengths of a single WGM and two WGMs are investigated. The results show that the RI sensitivity by only monitoring the resonance wavelength shift of the WGM (1, 28) is 72.9402 nm/RIU, which is higher than that (42.5211 or 45.8821 nm/RIU for different Wgap) of the WGM (0, 36). However, the approximate temperature sensitivities of 0.0730 and 0.0703 nm/K for WGM (0, 36) and WGM (1, 28) are respectively achieved by monitoring different WGMs. Thus, the RI and temperature changes are simultaneously measured by monitoring the resonance shifts of the two WGMs with a character matrix. In other words, the measurement of RI with less temperature influence is achieved by monitoring δλWGM with the compromising RI sensitivity. The proposed sensor has a potential application in simultaneous measurement of multi-variables, such as RI, temperature, humidity, stress, etc., by using more WGMs and is easy to integrate with other SOI devices.

A novel solution for the large view angle holographic head-mounted display (HHMD) is presented. Divergent light is used for the hologram illumination to construct a large size three-dimensional object outside the display in a short distance. A designed project-type lens with large numerical aperture projects the object constructed by the hologram to its real location. The presented solution can realize a compact HHMD system with a large field of view. The basic principle and the structure of the system are described. An augmented reality (AR) prototype with the size of 50 mm×40 mm and the view angle above 60° is demonstrated.

In this paper, a floating 3D display system that consists of an autostereoscopic display and a symmetric cemented doublet (SCD) is demonstrated. 3D image is generated by the autostereoscopic display and it floats into a free space by the use of the SCD. Furthermore, SCD is designed to correct the chromatic aberration and distortion of the floating system. To confirm the feasibility of the proposed system, simulations and experiments are performed, and the results are comparatively discussed with those of the conventional system.

Integral imaging is a promising 3D visualization technique for reconstructing 3D medical scenes to enhance medical analysis and diagnosis. However, the use of lens arrays inevitably introduces flipped images beyond the field of view, which cannot reproduce the correct parallax relation. To avoid the flipping effect in optical reconstruction, a twice-imaging lens array based integral display is presented. The proposed lens arrangement, which consists of a light-controlling lens array, a field lens array and an imaging lens array, allows the light rays from each elemental image only pass through its corresponding lens unit. The lens arrangement is optimized with geometrical optics method, and the proposed display system is experimentally demonstrated. A full-parallax 3D medical scene showing continuous viewpoint information without flipping is reconstructed in 45° field of view.

When employing the light field method with standard lens array and the holographic functional screen (HFS) to realize the tabletop three-dimensional (3D) display, the viewing area of the reconstructed 3D images is right above the screen. As the observers sit around the table, the generated viewpoints in the middle of the viewing area are wasteful. Here, a 360-degree viewable light-field display system is demonstrated, which can present 3D images to multiple viewers in ring-shaped viewing range. The proposed display system consists of the HFS, the aspheric conical lens array, a 27-inch LCD with the resolution of 3840×2160, the LEDs array and the Fresnel lens array. By designing the aspheric conical lens, the light rays emitting from the elemental images forms the viewpoints in a ring-type arrangement. And the corresponding coding method is given. Compared with the light field display with standard lens array, the viewpoint density is increased and the aliasing phenomenon is reduced. In the experiment, the tabletop light-field display based on aspheric conical lens array can present high quality 360-degree viewable 3D image with the right perception and occlusion.

In this paper, we numerically investigate the mid-infrared supercontinuum (SC) generation in a suspended ${{\rm As}_2}{{\rm Se}_3}$As2Se3 ridge waveguide, which is designed with the two zero-dispersion wavelengths. Simulation results show that when the pump pulses at wavelength 3.3 µm with width of 100 fs and peak power of 900 W are launched into the anomalous dispersion region of the designed waveguide with a length of 0.87 mm, the SC can be generated in the wavelength range from 1.76 to 14.42 µm (more than three octaves), extending deep into the "fingerprint" region. The stability of the generated SC is confirmed by the first-order coherence. Moreover, we demonstrate the performance of the SC-based frequency comb by assuming a 50 pulse pump source at a repetition rate of 100 MHz.

Three-dimensional (3D) light field display, as a potential future display method, has attracted considerable attention. However, there still exist certain issues to be addressed, especially the capture of dense views in real 3D scenes. Using sparse cameras associated with view synthesis algorithm has become a practical method. Supervised convolutional neural network (CNN) is used to synthesize virtual views. However, such a large amount of training target views is sometimes difficult to be obtained and the training position is relatively fixed. Novel views can also be synthesized by unsupervised network MPVN, but the method has strict requirements on capturing multiple uniform horizontal viewpoints, which is not suitable in practice. Here, a method of dense-view synthesis based on unsupervised learning is presented, which can synthesize arbitrary virtual views with multiple free-posed views captured in the real 3D scene based on unsupervised learning. Multiple posed views are reprojected to the target position and input into the neural network. The network outputs a color tower and a selection tower indicating the scene distribution along the depth direction. A single image is yielded by the weighted summation of two towers. The proposed network is end-to-end trained based on unsupervised learning by minimizing errors during reconstructions of posed views. A virtual view can be predicted in a high quality by reprojecting posed views to the desired position. Additionally, a sequence of dense virtual views can be generated for 3D light-field display by repeated predictions. Experimental results demonstrate the validity of our proposed network. PSNR of synthesized views are around 30dB and SSIM are over 0.90. Since multiple cameras are supported to be placed in free-posed positions, there are not strict physical requirements and the proposed method can be flexibly used for the real scene capture. We believe this approach will contribute to the wide applications of 3D light-field display in the future.

Spectral compression (SPC) can be used for generating narrow bandwidth and wavelength-tunable light sources, which have important applications in optical communication system, spectroscopy, and nonlinear microscopy. In this paper, we numerically demonstrate the high-degree SPC of the chirp-free femtosecond pulse at wavelength 2.4 μm in a 6-cm long adiabatically suspended silicon waveguide taper. The silicon waveguide taper is designed with a dispersion-increasing profile along the propagation distance z. Simulation results show that the SPC factor can be up to 10.9, along with the brightness-enhanced factor of 8.0 and negligible sidelobe. The impacts of the higher order dispersion, higher order nonlinearity, losses (including linear and nonlinear loss), and variation of Kerr nonlinear coefficient along z on the SPC are also investigated. It is found that variation of Kerr nonlinear coefficient γ(z) and linear loss are the dominant perturbation to the degradation of the SPC performance.