Integral Imaging 3D Display Research Articles

A 2D/3D convertible integral imaging display with enhanced depth of field

Depth of field (DOF) enhancement and two-dimensional (2D)/three-dimensional (3D) convertible display are important research areas of integral imaging 3D display. However, there is no accurate definition of DOF in existing integral imaging 3D displays, and it is difficult to realize DOF enhancement and 2D/3D convertible display simultaneously. In this paper, we propose a DOF analysis method for integral imaging 3D display, and derive an accurate definition of DOF by analyzing the voxel formation mechanism and the minimum resolution angle of the human eyes. Then a 2D/3D convertible integral imaging display with an enhanced DOF is proposed based on the definition of the DOF. The DOF enhancement and different display modes of 2D and 3D are realized by using two sets of dual-state optical components, including polymer dispersed liquid crystal (PDLC) films and liquid crystal micro-lens arrays (LCMLAs). When PDLC film in one set is scattering and LCMLA has the optical properties of a micro-lens array, while PDLC film in the other set is transparent and LCMLA has the optical properties of a flat glass at the same time, the system operates in 3D display modes. Two sets of DOFs are formed in turns and spliced to enhance the whole DOF based on the persistence of vision. When only one PDLC film is scattering and two LCMLAs both have the optical properties of a flat glass, the system realizes 2D display. The experiments on the 2D/3D convertible integral imaging display prototype verify that the DOF is enhanced to 1.71 times and 2D/3D convertible display is realized simultaneously compared with the display based on a conventional micro-lens array. The proposed display has potential for applications in areas such as education and medical care.

Fabrication of microlens arrays on curved substrates for large viewing angle integral imaging 3D display

Curved integral imaging for three-dimensional (3D) displays is well-known for offering an immersive experience and a wider display field of view. Presently, numerous techniques for fabricating curved microlens arrays (curved MLA) have been documented. Nevertheless, the majority of prior research relied on indirect approaches, like utilizing flexible substrates or creating molds. This paper introduces a method for directly fabricating microlens arrays (MLAs) on curved quartz glass. Well-designed arrays of controlled adhesive droplets were created on a hydrophilic-hydrophobic patterned surface. The resulting MLAs, manufactured on a curved substrate with a radius of 10 cm and dimensions of 5 cm × 5 cm, exhibit an 826.5 μm diameter, 56 μm inter-lens spacing, and a 4.5 mm focal length. The effective area of the curved MLA measures 45.8 mm × 45.8 mm. The study encompasses the design of a 2D elemental image and its integration with the curved MLA to achieve a compelling 3D display effect. The lateral viewing range is 2.2 cm. Notably, the field of view angle for the MLA, fabricated on a curved substrate, reached 11.2°, surpassing that of planar MLAs. The imaging system delivers an extensive field of view and attains a realistic 3D stereoscopic display effect. This method, employing various masks, facilitates the rapid fabrication of MLAs on substrates with diverse curvatures and sizes.

Viewing-Angle-Enhanced and Dual-View Compatible Integral Imaging 3D Display Based on a Dual Pinhole Array.

Conventional integral imaging (InIm) three-dimensional (3D) display has the defect of a small viewing angle and usually presents a single 3D image. In this paper, we propose a viewing-angle-enhanced and dual-view compatible InIm 3D display system. The crosstalk pixel areas within the conventional elemental images (EIs) that result in image crosstalk were effectively utilized either for viewing angle enhancement or for dual-view 3D display. In the viewing-angle-enhanced 3D display mode, a composite elemental image (CEI) that consisted of a normal EI and two view-enhanced EIs was imaged by a dual pinhole array and formed an extended 3D viewing area. A precisely designed mask array was introduced to block the overlapped rays between adjacent viewing areas to eliminate image crosstalk. While in the dual-view 3D display mode, a CEI was composed of image information of two different 3D scenes. With the help of the dual pinhole array and mask array, two different 3D images were reconstructed for the left and right perspectives. Experiments demonstrated that both the left and right sides were increased by 6 degrees from the conventional 3D viewing angle, and also, a dual-view 3D display effect that retains the same viewing angle as the conventional system was achieved. The proposed system has a compact structure and can be freely switched between two display modes.

P‐145: Late‐News Poster: Integral Imaging 3D Display Based on Top‐hat Diffusing Screen

We propose an integral imaging 3D display based on top‐hat diffusing screen. The integral imaging 3D display consists of a 2D display, a micro‐lens array, and a top‐hat diffusing screen. The top‐hat diffusing screen is composed of multiple elemental lenses with different pitches. The light rays pass through the top‐hat diffusing screen to form a regular light spot, and the light intensity distribution of the light spot is top‐hat type. This can make the 3D image smooth and natural. The experimental results verify the feasibility of the proposed integral imaging 3D display.

Enhanced depth of field of integral imaging display using bifocal microlens array fabricated by two‐step lithography

AbstractDue to the limitation of traditional microlens arrays (MLAs) in integral imaging display, the depth of field (DOF) is restricted in space and the center depth plane is difficult to extend in a large range. Here, we propose a microfabrication method based on bifocal MLAs to improve DOF. The bifocal MLAs for extended DOF were fabricated by using two‐step photolithography and thermal reflow. This method allows diverse microlenses of high to low numerical aperture to achieve high spatial resolution as well as accurate depth estimation. Microlenses of different focal lengths were simultaneously deposited on a substrate by repeated photolithography with multiple photomasks with alignment mark to define micro‐posts of different thicknesses. Hexagonally packaged bifocal MLAs clearly show the DOF extended from 0.004 to 4.908 mm for 57.6 μm in lens diameter, and their corresponding object distance ranges from 0.125 to 0.165 mm. Based on the proposed scheme, this method provides potential applications in integral imaging 3D display or light field display.

4: Wide‐Viewing Angle Integral Imaging 3D Display System Based on Aspherical Compound Lens Array

4: Wide‐Viewing Angle Integral Imaging 3D Display System Based on Aspherical Compound Lens Array

Large-Area and Rapid Fabrication of a Microlens Array on a Flexible Substrate for an Integral Imaging 3D Display.

A curved integral imaging three-dimensional (3D) display attracts a lot of interest due to its enhanced 3D sense of immersion and wider viewing angle. In this paper, a microlens array (MLA) based on a flexible poly(ethylene terephthalate) (PET) substrate was achieved by a straightforward, rapid, and low-cost technique. The reactive ion etching (RIE) process treated PET/CYTOP covered with a flexible mask to generate a hydrophilic-hydrophobic patterned surface. The well-designed arrays of confined adhesive droplets with a controlled geometry on a hydrophilic-hydrophobic patterned surface were formed using the blade-coating method. A flexible MLA with a diameter of 820 μm, a size of 5.3 cm × 5.1 cm, and a radius of curvature of 25 cm was fabricated and combined with a curved two-dimensional (2D) monitor to realize a lateral viewing range of 6.4 cm at a viewing distance of 25 cm, which is 4 times larger than with flat integral imaging 3D display system. The flexible MLA has the advantages of a controllable lens profile and large pitch, and it can be manufactured on a large scale. In addition, it provides a large viewing angle for the reconstructed 3D image.

Integral imaging 3D display with enhanced viewing angle using two tilted folding mirrors

We propose a viewing-angle-enhanced integral imaging (InI) 3D display using two tilted folding mirrors. The tilted folding mirror generates a corresponding additional virtual tilted micro lens array (MLA) adjacent to the real MLA, which is similar to a curved MLA structure. The two virtual tilted MLAs emit tilted light beams with larger tilt angles than conventional InI, which results in an enhanced viewing angle. A modified elemental image synthesis algorithm is proposed to match the proposed scheme. Visualization simulation and optical experiment are performed to verify the proposed method.

29.5: Enhanced depth of field of integral imaging display using bifocal microlens array fabricated by two‐step lithography

Due to the limitation of traditional microlens arrays (MLAs) in integral imaging display, the depth of field (DOF) is restricted in space and the center depth plane are difficult to extended in a large range. Here we propose a microfabrication method based on bifocal MLAs to improve DOF. The bifocal MLAs for extended DOF was fabricated by using two‐step photolithography and thermal reflow. This method allows diverse microlenses of high to low numerical aperture to achieve high spatial resolution as well as accurate depth estimation. Microlenses of different focal lengths were simultaneously deposited on a substrate by repeated photolithography with multiple photomasks with alignment mark to define micro‐posts of different thicknesses. Hexagonally packaged bifocal MLAs clearly show the DOF extended from 0.004 mm to 4.908 mm for 57.6 �m in lens diameter and their corresponding object distance ranges from 0.125 mm to 0. 165 mm. Based on the proposed scheme, this method provides potential applications in integral imaging 3D display or light field display.

P‐7.20: Depth‐enhanced Integral Imaging 3D Display System

A depth-enhance integral imaging (InIm) 3D display system is proposed. Two InIm 3D displays that are placed vertically and be used in the proposed system by combining a transmissive mirror device (TMD) and a semi-transparent mirror (STM) to enhance the depth. Due to the distance between the two InIm 3D displays and the TMD is different, so the 3D display proposed achieves the extension of depth of field (DOF). The experimental results demonstrate the validity of our proposed system.

Design and calibration of curved and see-through integral imaging 3D display

Design and calibration of curved and see-through integral imaging 3D display

Dual-side see-through integral imaging 3D display system based on lens array holographic optical element

We propose a dual-side see-through integral imaging 3D display based on a lens array holographic optical element (LAHOE). The display system consists of two projectors and a LAHOE. The LAHOE is fabricated according to the theory of reflective volume holograms. An interference pattern is formed by a plane-wave beam and a spherical-wave array beam, and the interference pattern is recorded into a photopolymer material. Thus, the LAHOE is formed. When a reference beam is projected into the LAHOE, the wavefront of a convex micro-lens array is reconstructed. When a phase conjugation reference beam is projected into the LAHOE, the wavefront of a concave micro-lens array is reconstructed. So, the LAHOE possesses the optical properties of a convex micro-lens array and a concave micro-lens array. The proposed display is developed using integral imaging principle and it realizes dual-side see-through integral imaging 3D display.

A real‐time interactive rendering method for 360° tabletop integral imaging 3D display

AbstractIn this paper, a rendering method for interactive tabletop integral imaging 3D display is proposed to present interactive 3D graphics to users 360° around the display in real‐time. By transforming the viewpoint plane and the elemental image array (EIA) plane with a parallel backward ray‐tracing technique according to the recognized gestures, a high‐efficient rendering for interactive 3D contents can be achieved, thus, the 3D graphics can be manipulated to be displayed on the tabletop in real‐time. Compared with the previous methods that all viewpoint images should be generated first, the proposed method can generate the interactive EIAs that contain all viewpoint information directly, which makes the interactive rendering more efficient. A gesture‐based interactive tabletop integral imaging 3D display prototype is built using an 8‐K (7680 × 4320) pixel resolution LCD. Experimental results show that the proposed interactive rendering method can achieve a short response time of less than 40 ms and high recognition accuracy of over 95% for different spatial hand gestures.

High‐efficient rendering to generate annular sector elemental image array for tabletop integral imaging three‐dimensional display

AbstractIn this paper, we propose a high‐efficient rendering method based on the backward ray‐tracing technique to generate the annular sector elemental image array (ASEIA), which can form an ideal annular viewing zone for tabletop integral imaging 3D display. In the rendering process, different pixels in each annular sector elemental image are associated with different viewpoints by the backward rays in one rendering step. Therefore, the ASEIA can be obtained directly without capturing single‐viewpoint images from all 360‐degree directions, which improves rendering efficiency. Compared with the conventional ASEIA generation method, the rendering time is reduced and is independent of the viewpoint number. The experimental results show the feasibility of the proposed method.

P‐75: Tabletop Integral Imaging 3D Display with Annular Viewing Zone

An annular viewing zone‐based tabletop integral imaging 3D display is presented. By adjusting the shape of the elemental images, viewing sub‐zone with annular sector distribution can be generated. Therefore, an annular viewing zone can be created in a time‐multiplexing way. The motion parallaxes of the proposed display are smooth.

Large-scale microlens arrays on flexible substrate with improved numerical aperture for curved integral imaging 3D display

Curved integral imaging 3D display could provide enhanced 3D sense of immersion and wider viewing angle, and is gaining increasing interest among discerning users. In this work, large scale microlens arrays (MLAs) on flexible PMMA substrate were achieved based on screen printing method. Meanwhile, an inverted reflowing configuration as well as optimization of UV resin’s viscosity and substrate’s surface wettability were implemented to improved the numerical aperture (NA) of microlenses. The results showed that the NA values of MLAs could be increased effectively by adopting inverted reflowing manner with appropriate reflowing time. With decreasing the substrate’s wettability, the NA values could be increased from 0.036 to 0.096, when the UV resin contact angles increased from 60.1° to 88.7°. For demonstration, the fabricated MLAs was combined to a curved 2D monitor to realize a 31-inch curved integral imaging 3D display system, exhibiting wider viewing angle than flat integral imaging 3D display system.

Effect of Viewpoints on the Accommodation Response in Integral Imaging 3D Display

Integral imaging three-dimensional (3D) display provides quasi-continuous viewpoints within a certain viewing angle. A single human eye can obtain several parallax images corresponding to the viewpoints. In this paper, we studied the effect of viewpoints received by a single human eye on the accommodation response when viewing the 3D image reconstructed by integral imaging 3D display. We analyzed the viewpoints distribution of an integral imaging 3D display and the correspondence relationship between the viewpoints and pixels information in elemental image array. In the experiment, the accommodation responses of human eyes when viewing the 3D image with different viewpoint quantities and dimensions are measured. The statistical results reveal that the more viewpoints received by a single human eye, the closer the accommodation response of the 3D image is to that of the real target. This tendency is obvious when the viewpoint quantity reduces from 10 × 10 to 6 × 6. For situations of 2 × 2 and 1 × 1 viewpoint, the accommodation response is unstable and different from the real target. When considering the viewpoint dimensions, two-dimensional viewpoints can provide a more natural accommodation response than one-dimensional viewpoints do. For the one-dimensional viewpoint situation, the horizontal arranged viewpoints and vertical arranged viewpoints have no statistical discrepancy.

Bionic-compound-eye structure for realizing a compact integral imaging 3D display in a cell phone with enhanced performance.

A bionic-compound-eye structure (BCES), which is a substitute of a microlens array, is proposed to enhance the performance of integral imaging (II) 3D display systems. Hexagonal ocelli without gaps and barriers are predesigned to obtain a continuous image, high-resolution, and uniform parallax. A curved substrate is designed to enhance the viewing angle. In addition, ocelli are fused with the substrate to form a relief structure, BCES. When they are placed above a normal display, continuous and full-parallax 3D images with 150 µm effective resolution and a 28° horizontal, 22° vertical viewing angle could be achieved, about twice as much as that of normal systems. The weight of the BCES is 31 g, and the thickness of the whole system is 22 mm; thus, the BCES-based II (BCES-II) is very compact. In addition, this structure can be easily integrated into a cell phone or iPad for compact quasi-2D and 3D adjustable display.

Electrically high-resistance liquid crystal micro-lens arrays with high performances for integral imaging 3D display

In this paper, we propose a high-resistance (Hi-R) liquid crystal (LC) micro-lens arrays (MLAs) with a low operating voltage and a controllable focal length for integral imaging (II) 3D display. The focal lengths of the Hi-R LC MLAs can be effectively controlled by applying different operating voltages and driving frequencies. The experimental results indicate that the focal lengths can be adjusted from 4.27 mm to 2.88 mm when the operating voltage applied to the Hi-R LC MLAs increases from 1.8 Vrms to 2.8 Vrms at the driving frequency of 130 kHz. Compared with the II 3D display by using ITO circular-hole electrodes-based or Al circular-hole electrodes-based LC MLAs without Hi-R layer, the II 3D display based on the Hi-R LC MLAs with Al circular-hole electrodes can reveal clear 3D scenes at the corresponding center depth plane (CDP) when a low operating voltage is applied to the Hi-R LC MLAs. Furthermore, the generated elemental images with different depths can be reconstructed at different CDPs by electrically controllable focal lengths of the Hi-R LC MLAs, and these 3D scenes can be realized the switchable display in the same II 3D display system, which can effectively present the optical performance of the II 3D display.

Integral imaging-based 2D/3D convertible display system by using holographic optical element and polymer dispersed liquid crystal.

An integral imaging-based 2D/3D convertible display system is proposed by using a lens-array holographic optical element (LAHOE), a polymer dispersed liquid crystal (PDLC) film, and a projector. The LAHOE is closely attached to the PDLC film to constitute a projection screen. The LAHOE is used to realize integral imaging 3D display. When the PDLC film with an applied voltage is in the transparent state, the projector projects a Bragg matched 3D image, and the display system works in 3D mode. When the PDLC film without an applied voltage is in the scattering state, the projector projects a 2D image, and the display system works in 2D mode. A prototype of the integral imaging-based 2D/3D convertible display is developed, and it provides 2D/3D convertible images properly.