Full-color Holographic Display Research Articles

Ultrahigh-fidelity full-color holographic display via color-aware optimization

Holographic display offers the capability to generate high-quality images with a wide color gamut since it is laser-driven. However, many existing holographic display techniques fail to fully exploit this potential, primarily due to the system’s imperfections. Such flaws often result in inaccurate color representation, and there is a lack of an efficient way to address this color accuracy issue. In this study, we develop a color-aware hologram optimization approach for color-accurate holographic displays. Our approach integrates both laser and camera into the hologram optimization loop, enabling dynamic optimization of the laser’s output color and the acquisition of physically captured feedback. Moreover, we improve the efficiency of the color-aware optimization process for holographic video displays. We introduce a cascade optimization strategy, which leverages the redundant neighbor hologram information to accelerate the iterative process. We evaluate our method through both simulation and optical experiments, demonstrating the superiority in terms of image quality, color accuracy, and hologram optimization speed compared to previous algorithms. Our approach verifies a promising way to realize a high-fidelity image in the holographic display, which provides a new direction toward the practical holographic display.

Energy-efficient dispersion compensation for digital micromirror device

Due to the wave nature of light, the diffraction pattern generated by an optical device is sensitive to the shift of wavelength. This fact significantly compromises the digital micromirror device (DMD) in applications, such as full-color holographic display and multi-color fluorescence microscopy. The existing dispersion compensation techniques for DMD involve adding diffractive elements, which causes a large amount of waste of optical energy. Here, we propose an energy-efficient dispersion compensation method, based on a dispersive prism, for DMD. This method simulates the diffraction pattern of the optical fields reflected from the DMD with an angular spectrum model. According to the simulation, a prism and a set of optical components are introduced to compensate for the angular dispersion of DMD-modulated optical fields. In the experiment, our method reduced the angular dispersion, between the 532 nm and 660 nm light beams, by a factor of ∼8.5.

A Full-Color Holographic System Based on Taylor Rayleigh–Sommerfeld Diffraction Point Cloud Grid Algorithm

Real objects-based full-color holographic display systems usually collect data with a depth camera and then modulate the input light source to reconstruct the color three-dimensional scene of the real object. However, at present, the main problems of the real-time high quality full-color 3D display are slow speed, low reconstruction quality, and high consumption of hardware resources caused by excessive computing. Based on the hybrid Taylor Rayleigh–Sommerfeld diffraction algorithm and previous studies on full-color holographic systems, our paper proposes Taylor Rayleigh–Sommerfeld diffraction point cloud grid algorithm (TR-PCG), which is to perform Taylor expansion on the radial value of Rayleigh–Sommerfeld diffraction in the hologram generation stage and modify the data type to effectively accelerate the calculation speed and ensure the reconstruction quality. Compared with the wave-front recording plane, traditional point cloud gridding (PCG), C-PCG, and Rayleigh–Sommerfeld PCG without Taylor expansion, the computational complexity is significantly reduced. We demonstrate the feasibility of the proposed method through experiments.

Computer-generated full-color phase-only hologram using a multiplane iterative algorithm with dynamic compensation

Depth-division multiplexing (DDM) is a common method for full-color hologram generation. However, this method will result in uneven image-quality levels at different color channels of the original color image. In this paper, the DDM method with dynamic compensation is proposed for a full-color holographic display. Three monochromatic images of red (R), green (G), and blue (B) channels from the original color image are placed orderly at different positions (object planes) of the same optical axis; then, the complex amplitudes of the three object planes are iteratively updated in a designed order when a laser wavefront propagates between object planes and the hologram plane. In the iterative process, a dynamic compensation factor is added to the complex amplitude of each object plane, which can effectively balance the quality level of the reconstructed image in each color channel. As a result, the image quality of a full-color object is improved. Numerical simulation and optical experiments are carried out to verify the method's feasibility.

Aberration-corrected full-color holographic augmented reality near-eye display using a Pancharatnam-Berry phase lens.

We present a full-color holographic augmented reality near-eye display using a Pancharatnam-Berry phase lens (PBP lens) and its aberration correction method. Monochromatic and chromatic aberrations of the PBP lens are corrected by utilizing complex wavefront modulation of the holographic display. A hologram calculation method incorporating the phase profile of the PBP lens is proposed to correct the monochromatic aberration. Moreover, the chromatic aberration is corrected by warping the image using the mapping function obtained from ray tracing. The proposed system is demonstrated with the benchtop prototype, and the experimental results show that the proposed system offers 50° field of view full-color holographic images without optical aberrations.

Full color holographic display system based on intensity matching of reconstructed image.

In this paper, a full color holographic display system based on the intensity matching of the reconstructed image is proposed. The system consists of three color collimated beams, three spatial light modulators (SLMs), three beam splitters, three lenses, three irises, a prism and a receiving screen. The three SLMs are used to load three color holograms, respectively. In order to eliminate the undesirable light in the reconstructed images and adjust the light intensities, the irises which contain two functions of both light intensity attenuation and aperture variation are cleverly produced. Finally, by using the prism, three color images can be coincident on the receiving screen. Experimental results verify the feasibility of the proposed system.

Chromatic-dispersion-corrected full-color holographic display using directional-view image scaling method.

A novel directional-view image scaling method that corrects chromatic dispersion and enhances the quality of three-dimensional (3D) images reconstructed by a full-color holographic display system is proposed. When the 3D information of the real scene is acquired through the integral imaging pickup method, the orthographic projection image is reconstructed. Then, each directional-view image is separated and synthesized onto the computer-generated hologram. To correct the chromatic dispersion of the full-color holographic 3D display, each directional-view image is scaled depending on the relation between the different wavelengths of single-channel holograms and resolutions of the sub-holograms. According to the optical experimental results, it can be concluded that the proposed method is an effective way of producing full-color holographic images from an orthographic projection image through a simple process.

Full-color holographic 3D display using slice-based fractional Fourier transform combined with free-space Fresnel diffraction.

The fractional Fourier transform (FRT) has been used for computing holograms in holographic displays due to its continuity of describing wave diffraction in the near field and far field. In this study, we propose a method to realize a full-color holographic 3D display with combined use of the FRT and the free-space Fresnel diffraction. A slice-based optical configuration and the calculation algorithm of the FRT are proposed for generating phase-only holograms of full-color 3D objects. Sequential phase-only holograms are generated for reducing the speckle noise of reconstructed images by the time-averaging effect. Free-space Fresnel diffraction is used for 3D image reconstruction from the generated holograms. The relationship between the fractional orders of different color channels and the free-space Fresnel diffraction distance is analyzed. Chromatic aberrations caused by different wavelengths of RGB lasers are also compensated. A full-color holographic display system using a reflective phase-only spatial light modulator (SLM) is established. Both the numerical and optical reconstruction results demonstrate the feasibility of the proposed method.

Full-color holographic projection display system featuring an achromatic Fourier filter.

We propose a full-color complex holographic display system design comprised of three R/G/B amplitude-only spatial light modulators and an achromatic Fourier filter. A key feature of the design is a single achromatic Fourier bandpass filter for robust axial R/G/B color matching, whereby the R/G/B holographic image light fields can be three-dimensionally aligned. The synthesis algorithm producing the full-color computer-generated holograms for this system is described and a full-color optical reconstruction of the designed holographic three-dimensional images is experimentally demonstrated.

Full-color holographic display with increased-viewing-angle [Invited

Among the important features of holographic displays are the wide viewing angles and the full color of the reconstructed images. The present work focuses on achievement of both features. We propose an increased-viewing-angle full-color holographic display using two tiled phase-only spatial light modulators (SLMs), a 4f concave mirrors system, and a temporal-spatial multiplexing method. The 4f optical system consists of two concave mirrors and serves to increase the viewing angle. A temporal-spatial multiplexing synchronization control (TSMSC) method is developed to achieve a full-color image and to remove the color crosstalk of the image. We calculate RGB phase-only holograms of a computer-generated color pyramid by using a slice-based Fresnel diffraction algorithm. The experimental results indicate that the proposed display system is feasible to reconstruct a full-color holographic 3D image with a viewing angle of 12.8°, which is about 3.8 times wider than the viewing angle formed by a single SLM.

Progress on waveguide-based holographic video (Invited Paper)

This paper presents progress on the characterization of guided-wave light modulators for use in a low-cost holographic video monitor based on the MIT scanned-aperture architecture. A custom-built characterization apparatus was used to study device bandwidth, RGB operation, and linearity in an effort to identify optimal parameters for high bandwidth, GPU-driven, full-color holographic display.

Reducing the memory usage for effectivecomputer-generated hologram calculation using compressed look-up table in full-color holographic display

A fast algorithm with low memory usage is proposed to generate the hologram for full-color 3D display based on a compressed look-up table (C-LUT). The C-LUT is described and built to reduce the memory usage and speed up the calculation of the computer-generated hologram (CGH). Numerical simulations and optical experiments are performed to confirm this method, and several other algorithms are compared. The results show that the memory usage of the C-LUT is kept low when number of depth layers of the 3D object is increased, and the time for building the C-LUT is independent of the number of depth layers of the 3D object. The algorithm based on C-LUT is an efficient method for saving memory usage and calculation time, and it is expected that it could be used for realizing real-time and full-color 3D holographic display in the future.

Computer-generated kinoforms of real-existing full-color 3D objects using pure-phase look-up-table method

A computational method based on pure-phase look-up-table (LUT) is proposed for generating kinoforms of full-color real-existing three-dimensional (3D) objects. The principle of the pure-phase LUT method is described. 3D depth as well as color information of a full-color 3D object is obtained by the full-color 3D profile measurement approach based on binocular vision. The obtained full-color 3D data is decomposed into red (R), green (G), and blue (B) channels, and kinoforms of each channel are calculated from the depth map and color information of the corresponding channel using the pure-phase LUT method. In order to reduce the speckle noise of reconstructed full-color 3D image, sequential kinoforms of each color channel are generated by adding dynamic-pseudorandom phase factor into the object domain. Numerical reconstruction and optical reconstruction with a phase-only spatial light modulator (SLM) show that, with the proposed method, full-color holographic 3D display of real-existing full-color 3D objects is available.

Correction method for phase-modulation deviation of liquid crystal spatial light modulator in full-color holographic display

It is feasible to realize full-color holographic display based on liquid crystal spatial light modulator by use of multi-wavelength illumination combined with time division multiplexing (TDM) or space division multiplexing (SDM). However, the modulation characteristics of liquid crystal spatial light modulator (LC-SLM) vary with the wavelength of incident laser beam. Especially, the non-linearity and the modulation-depth mismatch of phase modulation curve are the important factors influencing the reconstruction quality of phase hologram in full-color holographic display. In order to solve this problem, a novel method is proposed to correct the gray-scale of phase holograms in the RGB channels with the established gray-mapping model according to the phase modulation curves measured under different wavelengths, and compensate the effects of non-linearity and the modulation-depth mismatch of phase modulation curves. Analysis of numerical and optical reconstruction results are carried out. It is verified that the method is effective to improve the qualities of reconstructed images in the RGB channels.