2D-3D switchable display based on a passive polymeric lenticular lens array and electrically suppressed ferroelectric liquid crystal

Switchable liquid crystal lenticular microlens arrays based on photopolymerization-induced phase separation for 2D/3D autostereoscopic displays

Conventionally, the fabrication of liquid crystal lenticular microlens arrays (LCLMLAs) is complicated and costly. Here, we demonstrate a one-step fabrication technique for LCLMLAs, which is prepared through the photopolymerization-induced phase separation in the LC/polymer composite. The LCLMLAs possess both polarization-dependent and electrically tunable focusing properties. Furthermore, we construct a 14-view 2D/3D switchable autostereoscopic display prototype based on a 2D LCD panel and the prepared LCLMLA, which has a viewing angle of 14° and a crosstalk of 46.2% at the optimal viewing zone. The proposed LCLMLAs have the merits of simple fabrication, large-scale production, and low cost.

Fast response electrically controlled liquid crystal lens array for high resolution 2D/3D switchable display

A fast response electrically controlled liquid crystal (LC) lens array is revealed. In order to realize the fast response, a double LC layer structure is adopted. The fabricated LC lens array has a small pitch of 310µm and LC layer with a thickness of 50μm. Experimental results show that the focal length of the LC lens array can be continuously adjusted by low driving voltage (∼6.5V_rms), and the shortest focal length is 0.5mm. The switching between 2D display and 3D display is realized by controlling the voltage off and on state of the LC lens array. Experimental result shows that the 2D/3D switchable display has a fast response time of 16ms. The short pitch LC lens array is expected to be used in high-resolution 2D/3D switchable display.

Liquid crystal microlens array with positive and negative focal lengths based on a patterned electrode

A liquid crystal microlens array (LCMLA) with positive and negative focal lengths based on a ring-array patterned electrodes is demonstrated. By carefully designing patterned electrodes with a circular electrode array area and outer ring electrode region area, the switching of the positive and negative lens effect can be easily achieved in a single cell. A positive lens effect appeared when the voltage was applied to the outer ring electrode region and the top substrate. The focal length changed from infinity to 1 mm as the voltage varied from 0 to 3V_rms. A negative lens effect occurred when the voltage was applied to the circular electrode array and the top substrate. The focal length varied from infinity to -1mm when the voltage changed from 0 to 2V_rms. The imaging properties of the LCMLA at different voltages are evaluated. Our LCMLA, with simple structure, low driving voltage, and good stability, has potential applications in optical communication, imaging processing, and displays.

Realization of inversely designed metagrating for highly efficient large angle beam deflection

Directional emission source is one of the key components for multiple-view three-dimensional display. It is hard to achieve high efficiency and large deflection angle direction sources via geometric optics due to the weak confinement of light. The metasurface especially metagrating provides a promising method to control light effectively. However, the conventional forward design methods for metasurface are inherently limited by insufficient control of Bloch modes, which causes a significant efficiency drop at a large deflection angle. Here, we obtained high efficiency large deflection angle metagratings by realizing the constructive interferences among the propagation Bloch modes and enhancing the outcoupling effect at the desired diffraction order. The grating structures that support the coupling of Bloch modes were designed by an inverse design method for different incident wavelengths, and the total phase response of a supercell can be tailored. For a red (620 nm) incident light, the theoretical deflection efficiency of a silicon metagrating can be higher than 80% from 30° to 80°. The experimental deflection efficiency can achieve 86.43% for a 75° deflection metagrating. The matched simulation and experimental results strongly support the reliability of developed algorithm. Our inverse design approach could be extended to the green (530 nm) and blue (460 nm) incident light with titanium dioxide metagratings, with theoretical deflection efficiency of over 80% in a large deflection angle range of 30° to 80°. Considering the multiple visible wavelength deflection capability, the developed algorithm can be potentially applied for full color three-dimensional display, and other functional metagrating devices based on different dielectric materials.

Fast responsive 2D/3D switchable display using a liquid crystal microlens array

A fast responsive two-dimensional/three-dimensional (2D/3D) switchable display is demonstrated based on an active liquid crystal (LC) microlens array and a twisted nematic (TN) cell. Compared with the traditional LC microlens array, the fabricated LC microlens array has more ideal phase profile and better focusing effect. The TN cell can switch the polarization direction of the incident light with a very short switching time (4.3 ms) and a small driving voltage (5V_rms). By introducing the tilted elemental image arrays and tilted LC lens array, the moiré patterns are eliminated. The fast switching of the 2D/3D display can be realized by applying or removing voltage to the TN cell. The fast responsive 2D/3D switchable display with the LC microlens array and the TN cell is thin and compact without moiré pattern compared with other 2D/3D switchable display devices.

Four-mode 2D/3D switchable display with a 1D/2D convertible liquid crystal lens array

A four-mode 2D/3D switchable display using a 1D/2D convertible liquid crystal (LC) lens array is proposed in this paper. The LC lens array is composed of two orthogonal LC lens arrays, with a λ/2 film in the middle to rotate the polarization by 90°. Based on the LC lens array, a four-mode 2D/3D switchable display is realized, which is switchable between the turn-off and turn-on states: when the operating voltage V₁ = 0, V₂ = 0, the display operates in mode I, which is 2D display; when the operating voltage V₁ = 0, V₂ = 0, the display operates in mode II, and the 3D display effect is in x direction; when the operating voltage V₁ = 0, V₂ = 0, the display operates in mode III, and the 3D display effect is in y direction; when the operating voltage V₁ = 0, V₂ = 0, the display operates in mode IV, the 3D display effect is in x-y plane. Experimental results indicate that the LC lens array has simple fabrication process, low operating voltage (∼5.4V), and short focal length. Moreover, based on the designed LC lens array, the 2D/3D switchable display shows no moiré pattern.

Multi-View 2D/3D Switchable Display with Cylindrical Liquid Crystal Lens Array

We propose a multi-view 2D/3D switchable display by using cylindrical liquid crystal (LC) lens array with a low operating voltage and fast response time. The cylindrical LC lens array is composed of three parts: the LC layer, a top-plane indium tin oxide (ITO) electrode, and bottom periodic strip ITO electrodes. In the voltage-off state, the cylindrical LC lens array is equivalent to a transparent glass substrate and the viewers can see a clear 2D image. In the 3D mode, the cylindrical LC lens array can be used as a cylindrical lens array under a suitable operating voltage. As a result, the 2D and 3D images can be switched according to the state of the cylindrical LC lens array. The experimental result shows that the 2D/3D switchable display with the cylindrical LC lens array has a wider viewing angle, has no moiré pattern, and is much thinner compared to the other 2D/3D switchable display devices.

Fast refocusing lens based on ferroelectric liquid crystals

Optical devices like virtual reality (VR) headsets present challenges in terms of vergence-accommodation conflict that leads to visual fatigue for the user over time. Lenses available to meet these challenges include liquid crystal (LC) lenses, which possess a response time in the millisecond range. This response time is slow, while accessing multiple focal lengths. A ferroelectric liquid crystal (FLC) has a response time in the microsecond range. In this article, we disclose a switchable lens device having a combination of the fast FLC-based polarization rotation unit and a passive polarization-dependent LC lens. A cascaded combination of three such lens units allows access to eight different focal points quite rapidly and can be a convenient device for VR applications.

2D/3D mixed frontal projection system based on integral imaging

Two-dimensional (2D)/three-dimensional (3D) convertible or mixed display is one of the most important factors for the fast penetration of 3D display into the display market. In this paper, we propose a 2D/3D mixed frontal projection system that mainly contains a liquid crystal micro-lens array (LCMLA) and a quarter-wave retarding film with pinholes (QWRF-P). The LCMLA exhibits the focusing effect or no optical effect depending on the polarization direction of the incident lights. The forward incident lights pass through the LCMLA without any bending. After passing through the QWRF-P twice, half of the backward lights change the polarization direction with 90°, and the other half remains. Using our designed system, different display modes, including 2D display, 3D display, and 2D/3D mixed display, can be realized. The unique feature of the proposed 2D/3D mixed frontal projection system is that it can switch the display modes by simply changing the image sources without the need of any active optical devices. Moreover, the proposed system is compact, simple and space-efficient, which is suitable for the application in glassless 3D cinema and home 3D theatre.

High-speed and robust infrared-guiding multiuser eye localization system for autostereoscopic display

In order to localize the viewers' eyes, a high-speed and robust infrared-guiding multiuser eye localization system was fabricated in this paper for a binocular autostereoscopic display, which can project a pair of parallax images to corresponding eyes. The system is composed of a low-resolution thermal infrared camera, a pair of high-resolution left and right visible spectral cameras, and an industrial computer. The infrared camera and the left visible spectral camera, and the left and right visible spectral camera, can both form the binocular vision system. The thermal infrared camera can capture the thermography images. The left and right visible spectral cameras can capture the left and right visible spectral images, respectively. Owing to the temperature difference between the face and background, the features of the face in thermography images are prominent. We use the YOLO-V3 neural network to detect the viewers' faces in thermography images. Owing to the different features of the pseudo and real faces in the infrared spectral, in the thermography images, the pseudo-faces can be easily eliminated. According to the positions and sizes of potential bounding boxes of the detected faces in the thermography images, the industrial computer can be guided to determine the left candidate regions in the left visible spectral image. Then, the industrial computer can determine the right candidate regions in the right visible spectral image. In the left candidate regions, the industrial computer detects the faces and localize the eyes by using the SeetaFace algorithm. The template matching is performed between the left and right candidate regions to calculate the accurate distance between the viewer and the system. The average detection time of the proposed method is about 3-8 ms. Compared with traditional methods, the localization time is improved by 86.7%-90.1%. Further, the proposed method is hardly influenced by the pseudo-faces and the strong ambient light.

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.

Polarization-dependent liquid crystalline polymeric lens array with aberration-improved aspherical curvature for low 3D crosstalk in 2D/3D switchable mobile multi-view display

We demonstrated a 2D/3D switchable mobile display using a polarization-dependent switching liquid crystalline polymeric (LCP) lens array film. In spite of short viewing distance and enough viewing window conditions provided by a small f-number lens for mobile displays, the 3D images when switched to the multi-view 3D mode showed a low crosstalk property owing to the improved lens aberration, as applying an aspherical lens curvature interface between the planar-convex LCP layer and the concave-planar isotropic polymer layer. Both 2D and 3D images were demonstrated based on a 5.5-inch quad high definition mobile display panel, where the binocular crosstalk of the 3D mode was 3.3%.