A conversion method of two-dimensional image into three-dimensional holographic display

A method is proposed for phase conjecture based on the intensity curve of a two-dimensional (2D) image by computing a polynomial equation. The intensity values of the 2D image, which represents the distance between the image detectors and the three-dimensional (3D) scene is converted to phase information by our method. The results of numerical calculation with phase conjecture are analyzed. And what’s more, the numerical reconstruction results with phase information obtained as initial phase factors of a complex object for Fresnel kinoform and dynamic pseudorandom-phase tomographic computer holography(DPP-TCH) are compared. The peak signal-to-noise ratio (PSNR) and correlation coefficient (CC) between the reconstructed images and original object are analyzed. An experimental system is designed for photoelectric holographic reconstruction based on phase-only liquid crystal spatial light modulator (LC-SLM) and mist screen. The electro-optical experimental results indicate that suppressed the speckle noise 3D images that can be observed with naked eye have been obtained.

Phase-only liquid crystal spatial light modulator (SLM) has been widely used for accurate phase-manipulation in holographic display, optical tweezers, lithography, etc. Due to the nonlinear optical response of liquid crystal and manufacturing defects, the grayscale-phase response could be different for every single SLM device. The calibration for phase modulation is needed for improving the performance of the SLM involved system. The principles of phase-only SLM are reviewed. The main phase calibration methods for SLM are discussed and compared.

A method for generating vector beams with higher-order states of polarization based on a setup with a one phase-only liquid crystal spatial light modulator is proposed. The polarization properties and double-slit interference of the higher-order vector beams were investigated in detail. The cross section intensity distributions were flower-like for higher-order vector beams when passing through a linear polarizer. Misplacements appeared in the double-slit interference fringes, which divided each fringe into several discrete parts, i.e., 2P-1 for P≥2, and 3 for P=1, where P is the polarization order number. When associated with optical petal orientations analysis of the beam spots behind a linear polarizer, the double-slit interference can be used to detect and analyze higher-order vector beams.

In this paper, a free-space wavelength-division demultiplexer utilizing single hologram displayed on a phase-only liquid crystal spatial light modulator is designed. The method combines different independently calculated 2π-holograms of each wavelength into a multi-level hologram utilizing the extended phase range of the spatial light modulator. The algorithm has low complexity, and can be employed to generate holograms that guide laser at different wavelengths to corresponding target devices with high speed. In combination with tracking technology, this method can be future applied in free space optics (FSO) link with wavelength division multiplexed (WDM) scheme for solving crosstalk problem.

Generation of vectorial optical fields with complex spatial distribution in the cross section is of great interest in areas where exotic optical fields are desired, including particle manipulation, optical nanofabrication, beam shaping and optical imaging. In this work, a vectorial optical field generator capable of creating arbitrarily complex beam cross section is designed, built and tested. Based on two reflective phase-only liquid crystal spatial light modulators, this generator is capable of controlling all the parameters of the spatial distributions of an optical field, including the phase, amplitude and polarization (ellipticity and orientation) on a pixel-by-pixel basis. Various optical fields containing phase, amplitude and/or polarization modulations are successfully generated and tested using Stokes parameter measurement to demonstrate the capability and versatility of this optical field generator.

An improved multiple independent iterative plane algorithm, based on a projection optimization idea, is proposed for the independent and arbitrary generation of one spot or multiple spots in a speckle-suppressed 3D work-area. Details of the mathematical expressions of the algorithm are given to theoretically show how it is improved for 3D spot generation. Both simulations and experiments are conducted to investigate the performance of the algorithm for independent and arbitrary 3D spot generation in several different cases. Simulation results agree well with experimental results, which validates the effectiveness of the algorithm proposed. Several additional experiments are demonstrated for fast and independent generation of four or more spots in the 3D space domain, which confirms the capabilities and practicalities of the algorithm further.

In this paper, we propose a method to implement a speckleless color dynamic three-dimensional holographic display by modulating amplitude and phase distribution simultaneously. Computer-generated holograms are calculated with an initial uniform phase, and the speckle noise of reconstructed images is suppressed effectively. We perform both numerical simulations and optical experiments to demonstrate the effectiveness of the proposed method. The numerical simulations show that the proposed method can achieve speckleless reconstruction and the optical experiments provide a good color dynamic display effect. It is expected that the proposed method could be widely applied to realize high-quality color dynamic holographic displays in the future.

This paper proposes a new method for three-dimensional dynamic holographic display that combines computer generated holography (CGH) and holographic stereogram. Theoretically, three-dimensional (3D) dynamic holographic display can be achieved by using CGH alone, however the application of CGH is still limited because large amounts of data processing and complex mathematical calculation of off-axis diffracted light field. A new method combining CGH and stereogram is proposed, since stereogram uses a set of 2D images instead of a 3D object, both the complexity of the calculation and the resolution requirements of spatial light modulator (SLM) is reduced. To prove the feasibility of this method, experiments of making hologram using this method is carried out and the result shows that 3D displaying with a view angle of 28 is achieved.

A holographic three-dimensional (3D) display is a recognized and ideal 3D display technology. In the field of holographic research, cylindrical holography with the merit of 360° field of view (FOV) has recently become a hot issue, as it naturally solves the problem of limited FOV in planar holography. The recently proposed approximate phase compensation (APC) method successfully obtains larger FOV and fast generation of segment cylindrical hologram (SCH) in the visible light band. However, the FOV of SCH remains limited due to its intrinsic limitations, and, to our best knowledge, the issue has not been effectively addressed. In this paper, the restricted conditions are first analyzed for the generation of SCH by the APC method. Then, an FOV expansion method is proposed for realizing a large FOV holographic display by gapless splicing of multi-SCH. The proposed method can successfully obtain larger FOV cylindrical holograms and effectively eliminate the splicing gaps; its effectiveness is verified by the results of numerical simulation and optical experiments. Therefore, the proposed method can effectively solve the FOV limitation problem of the APC method for the generation of SCH in the visible band, realize a large FOV 3D display, and provide a useful reference for holographic 3D display.

An experimental platform was built for the atmospheric turbulence simulation upon a liquid crystal spatial light modulator. The phase-only spatial light modulator is driven by a series of dynamic phase screens that have non-Kolmogorov turbulence characteristics. After passing through the simulated non-Kolmogorov turbulence, the angle-of-arrival (AoA) and light intensity of the laser beam were analyzed statistically. The variation trends of the AoA fluctuation and the scintillation index exhibited by the experimental results are in accordance with the theoretical predictions. Although there was some divergence between the experiments and theory that needs to be improved further, the experimental data demonstrate the feasibility of using the platform to simulate the turbulence influence on laser communication in the lab.

Simulators are being used to teach laparoscopic skills before residents get to the operating room. It is unknown whether the use of three-dimensional (3D) vision will facilitate laparoscopic training. Therefore, our objective was to compare the effectiveness of using 3D imaging over the traditional two-dimensional (2D) imaging to teach laparoscopic simulator skills to novice individuals and assess whether 3D imaging ameliorates laparoscopic performance for surgeons who have already adapted to working within a 2D surgical environment. This prospective study involved 36 surgical residents and students. Inexperienced participants included medical students and first- and second-year surgical residents (n = 25). Experienced participants included third- and fifth-year surgical residents (n = 11). Participants were tested on six laparoscopic skills using 2D or 3D imaging systems and then retested about 3 months later using the opposing imaging system. Evaluation of performance was based on the time elapsed to task completion and the errors committed during that time. The experienced participants performed better than the inexperienced participants regardless of the imaging system. Inexperienced participants initially tested using 2D imaging required significantly more time and/or made more errors to complete five of the six laparoscopic tasks compared to those initially tested using 3D imaging (p < 0.05). After initial testing on 3D imaging, inexperienced participants retested using 2D imaging performed significantly better on five of six tasks compared to the scores of inexperienced participants initially tested on 2D imaging (p < 0.05). In contrast, the inexperienced participants' retested on 3D after initial 2D imaging did not improve on any laparoscopic task compared to the scores of inexperienced participants initially tested on 3D imaging. Among the experienced participants, no significant difference in time or errors to task completion was observed under 2D imaging compared to 3D imaging during the first or second testing session. Our study indicates that 3D imaging offers significant advantages in the teaching of laparoscopic skills to inexperienced individuals.

In order to measure the local phase modulation characteristic of a phase-only reflective Liquid crystal spatial light modulator (LCSLM) and accurately evaluate the nonuniformity of phase modulation, a Twyman-Green interferometer is built to simultaneously measure the local phase modulation of multi-region in LCSLM. A series of carrier fringe patterns can be captured, which is modulated by the local control pattern loaded to the LCSLM. The phase distribution from all fringe patterns are extracted respectively with the Fourier transform method. By calculating the variance values of all phase values in each pixel position, a phase variance matrix is obtained. Then the regions of interests (ROIs) from the fringe pattern are extracted with the Otsu segmentation algorithm and the connected region labeling algorithm. At last, the phase modulation of local regions is obtained synchronously with the phase-shift algorithm based on Fourier transform method. The proposed method can greatly improve the measuring efficiency and reduce the environmental impact to great degree.

Holographic displays employing digital micromirror devices (DMDs) reconstruct 3D images at high diffraction orders. For LED displays, this geometry introduces large dispersion at the DMD surface, reducing image resolution and depth. This work proposes a color DMD LED holographic display with dispersion compensation utilizing an additional diffraction grating in an illumination module. The solution allows to obtain image depth up to 100mm, which is comparable to the one achieved by a liquid crystal spatial light modulator, where the limiting factor is spatial coherence of the source. Experimental comparison of the results obtained with the laser and LED source gives evidence of effective speckle noise reduction, even from a single frame.

Although most research on human facial attractiveness has used front-facing two-dimensional (2D) images, our primary visual experience with faces is in three dimensions. Because face coding in the human visual system is viewpoint-specific, faces may be processed differently from different angles. Thus, results from perceptual studies using front-facing 2D facial images may not be generalizable to other viewpoints. We used rotating three-dimensional (3D) images of women's faces to test whether men's attractiveness ratings of women's faces from 2D and 3D images differed. We found a significant positive correlation between men's judgments of women's facial attractiveness from 2D and 3D images (r = 0.707), suggesting that attractiveness judgments from 2D images are valid and provide similar information about women's attractiveness as do 3D images. We also found that women's faces were rated significantly more attractive in 3D images than in 2D images. Our study verifies a novel method using 3D facial images, which may be important for future research on viewpoint-specific social perception. This method may also be valuable for the accurate measurement and assessment of facial characteristics such as averageness, identity, attractiveness, and emotional expression.

After years of development, holography has become an essential tool of modern optics for many applications. Among them, holographic encryption and dynamic display are the two most typical applications. So far, however, only 2D targets or 2D images of 3D targets can be encrypted with holographic technology. The 3D multiplexing holographic technology of 3D multi‐targets has not yet been realized and holographic encryption of 3D multi‐targets is still a blank. Here, the conception of 3D orbital angular momentum (OAM) multiplexing holography is proposed, and holographic encryption of 3D multi‐targets is realized for the first time. This breaks the restriction that only 2D images can be encrypted in traditional holographic encryption. Furthermore, the results also show that the 3D OAM holography can be used in the dynamic display for 3D multi‐targets. In the experiment, the metasurface is used for taking its high‐resolution advantage in light field manipulation, and verify the feasibility of 3D OAM multiplexing holographic technology, holographic encryption of 3D multi‐targets, and holographic dynamic display of 3D targets. The work creates a precedent for the 3D multiplexing holography, encryption, and dynamic display technology of 3D multi‐targets, which brings real 3D life closer to humankind.