In this paper, we expand the eyebox size of lens-less holographic near-eye-display (NED) using passive eyebox replication technique that incorporates the spatial light modulator (SLM) and a holographic optical element (HOE). In holographic NEDs, the space-bandwidth product (SBP) of the SLM determines the exit pupil dimensions and corresponding eyebox size. The base eyebox is replicated in horizontal direction by using the horizontal high-order diffractions of the SLM under spherical wave illumination and multiplexed HOE combiner. The HOE combiner is used as a see-through reflective screen for the projected holographic virtual image, and it is fabricated based on two spherical divergent waves recording condition. When a digital blazed grating and a digital lens phase are added to the computed phase hologram sent to the SLM, two spatially separated, horizontal high-order diffraction terms with identical intensity and information can be used for eyebox expansion. When the eyebox size is expanded, the field-of-view (FOV) is not sacrificed; spherical divergence wave illumination alleviates the need for a tradeoff between FOV and eyebox size. Astigmatism distortion introduced during the HOE fabrication was counterbalanced by pre-correcting the target image using a computer-generated, holographic computation algorithm. The experimental results prove that the proposed prototype system is simple and effective to achieve distortion-free reconstruction of 3D virtual image and eyebox extension of lens less holographic NED.
The improvement of fill factor of holographic micromirror array (HMA) with holographic waveguide-type for threedimensional (3D) augmented-reality (AR) display system. Our proposed 3D AR system was created and briefly explain it; there have two the HOE optical film at in-and out coupler of the waveguide. In-coupler HOE is our fabricated HMA, it has a same role with optical microlens-array. HMA is integrate the displaying elemental image set (EIS) from micro display which EIS was generated by the integral imaging technology. The micro display has a 6 mm by 8mm size, 48single elemental images and micro display was located g distance from holographic waveguide which waveguide thickness was 5mm. EIS was displayed by micro display to holographic waveguide. HMA was stick with holographic waveguide and located in opposite side of waveguide and micro display. Micro display was display forward to holographic waveguide and fabricated HMA, then displayed EIS is reflected and integrated at the in-coupler HMA and integrated 3D image was through the holographic waveguide by HMA recorded angle. 3D images of internal reflect in the holographic waveguide was 1 time. 3D image was also reflected at the out-coupler HOE which role was same as optical mirror and reflect to observer’s eye. At least observer as the reconstructed images and real object out and reflects by out-coupler HOE.
In this paper, A full-color Denisyuk-type hologram using photopolymer has been recorded by the sequential exposure method. The photopolymer's optical characteristics show that inhibition periods of the photopolymer at three lasers are different in the same beam intensity. To increase the average diffraction efficiency of a full-color holographic optical element (HOE), the three lasers should be sequentially exposed to the photopolymer. The experimental results show that the average efficiency of a full-color reflection HOE is 59.6% and the standard deviation is 2.1. Also, the full-color hologram recorded in a one-layer photopolymer can reconstruct a high-quality image.
In this paper, a fast and efficient multiple wavefront recording planes method with parallel processing is proposed for enhancing the image quality and generation speed of point cloud-based holograms. The proposed method gives an optimized fixed active area to generate depth-related multiple WRPs to improve the calculation speed and enhance the color uniformity of full-color hologram. In other to parallel processing the ray tracing intermediate plane is created. This method is more effective when the number of depths is smaller, such as the RGB-D image.
We proposed an effective method of digital content generation for the holographic printer using the integral imaging technique. In order to print the three-dimensional (3D) holographic visualizations of the given object, a printed hologram consists of an array of sub-hologram (hogels) should be generated, before the hardware system of the holographic printer is run. There are mainly three parts related to the digital content generation. In the first part, the acquisition of the 3D point cloud object is applied and the second part provided an encoding of directional information extracted from the 3D object. The array of hogel is generated by implementing direction inversed computer-generated integral imaging plus phasemodulation for improvement of the content generation, and displayed on the reflective phase-only spatial light modulator (SLM) then recorded onto holographic material one-by-one in sequence, while motorized X-Y translation stage shifts the holographic material; so, the full-parallax holographic stereogram (HS) is printed on the holographic material and 3D visualization of the object is successfully observed. Numerical simulation and optical reconstructions are verified effective computation and image quality respectively.
KEYWORDS: Holograms, 3D image reconstruction, Image quality, Wavefronts, Computer generated holography, Digital holography, Holography, 3D modeling, Image enhancement, RGB color model
In this paper, a uniform multiple wavefront recording planes (UM-WRPs) method for enhancing the image quality of the RGB-depth (RGB-D) image hologram is proposed. The conventional multiple wavefront recording planes (M-WRPs) based full-color computer-generated hologram (CGH) have color uniformity problem caused by intensity distribution. In order to solve the problem, the proposed method generates depth-related wavefront recording planes (WRPs) to enhance the color uniformity and accelerate hologram generation using a fixed active area. Compared with conventional MWRPs methods, the quality of reconstructed images of this method is improved significantly. The image improvement of the proposed method is confirmed by numerical reconstruction
KEYWORDS: Clouds, 3D image processing, Cameras, 3D displays, Adaptive optics, 3D modeling, Image quality, Digital micromirror devices, Image resolution, Mirrors
A novel 360-degree integral-floating display based on the real object is proposed. The general procedure of the display system is similar with conventional 360-degree integral-floating displays. Unlike previously presented 360-degree displays, the proposed system displays the 3D image generated from the real object in 360-degree viewing zone. In order to display real object in 360-degree viewing zone, multiple depth camera have been utilized to acquire the depth information around the object. Then, the 3D point cloud representations of the real object are reconstructed according to the acquired depth information. By using a special point cloud registration method, the multiple virtual 3D point cloud representations captured by each depth camera are combined as single synthetic 3D point cloud model, and the elemental image arrays are generated for the newly synthesized 3D point cloud model from the given anamorphic optic system’s angular step. The theory has been verified experimentally, and it shows that the proposed 360-degree integral-floating display can be an excellent way to display real object in the 360-degree viewing zone.
Holographic optical element (HOE) have classically been designed using grating theory, logically so, since an HOE is a grating produced on film by two interfering beams of coherent light. This paper describes the development of full color HOE recorded on aspherical substrate using a photopolymer. The reflection HOE was evaluated by measuring the diffraction efficiencies of holographic volume gratings recorded individually at 633 nm, 532 nm, and 473nm wavelengths. The spectral characterization of the HOE, recorded using a combined single beam, and recorded using sequential beam, was carried out. Practical methods for fabrication of high efficiency aspheric HOE by single layer photopolymer were developed.
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