Liquid Crystal Lens Research Articles

Low-voltage tunable liquid crystal lens fabricated with self-assembled polymer gravel arrays.

A novel approach for fabricating liquid crystal (LC) lenses is presented. The approach involves the use of a photocurable prepolymer dispersed in a cell fabricated with vertically aligned substrates. A radial gradient UV irradiation intensity distribution is produced using a radial variable neutral density filter. Under UV irradiation, the prepolymer diffuses and is then polymerized on the substrate surfaces owing to vertical phase separation. After polymerization, the diameter of the self-assembled polymer gravel on the substrates has a radial gradient distribution, causing a radial gradient pretilt angle (RGPA) distribution on the substrates and producing LC lenses. By numerical simulation, RGPA LC lens has significantly lower supplied voltage than conventionally hole-patterned electrode (HPE) LC lens, and higher lens power. In the experiment, the fabricated RGPA LC lens with aperture size of 5 mm possesses a simple planar electrode structure, low operation voltage (< 4 V), small root mean square wavefront error (< 0.08 λ), and acceptable focusing quality. By the overdriving scheme, the switched-off time of the fabricated RGPA LC lens reaches 0.27 s. With the novel approach, low-voltage LC lenses with different optical aperture sizes can be easily fabricated.

Polarisation independent liquid crystal lenses and contact lenses using embossed reactive mesogens

AbstractLiquid crystal lenses have promise in optical systems owing to their tunability combined with low electrical power, cost, and weight. A good example of such a system is switchable contact lenses for the correction of age‐related presbyopia. Sufficiently large phase modulation can be done using nematic liquid crystals in a meniscus lens configuration. However, the birefringent materials are inherently polarisation dependent, usually requiring orthogonal polarisations to be focussed separately. A novel method is presented for producing polarisation independent lenses based on reactive mesogens. Results are presented for a 2‐level and 3‐level diffractive Fresnel lenses, and the promise of the technique for use in refractive lenses such as contact lenses is discussed.

Liquid Crystal Displays with Variable Viewing Angles Using Electric-Field-Driven Liquid Crystal Lenses as Diffusers

We propose a novel method for appropriately controlling the luminance distribution of liquid crystal displays (LCDs) for different usage environments by using electric-field-driven liquid crystal (ELC) lenses. The LCD systems are composed of quasi-collimated backlights (QCBLs), LC panels, and ELC lenses that are used as diffusers. To achieve a wide viewing angle, light is diffused with the ELC lenses by controlling its retardation with the voltage applied to the electrodes. For private use, a narrow viewing angle is achieved by turning the ELC lenses off so that the collimated light from the QCBLs passes directly through the liquid-crystal layer of the ELC lens and travels without diffusion. To validate the proposed method, we simulated the luminance distributions of the wide-view and narrow-view modes by using a finite difference method (FDM) and Taguchi’s design of experiments method. The simulation results show that the light distribution of the wide-view mode was 84.3% similar to the ideal Lambertian distribution and was wider than that of IPS-LCDs with wide viewing angle characteristics. In addition, the light distribution of the narrow-view mode had a full width at half maximum of 7°. The luminance of the exiting light at viewing angles of 20° and above was calculated to be close to 0.

Compact vari-focal augmented reality display based on ultrathin, polarization-insensitive, and adaptive liquid crystal lens

Despite the recent advances in augmented reality (AR), which has shown the potential to significantly impact on our daily lives by offering a new way to manipulate and interact with virtual information, minimizing visual discomfort due to the vergence–accommodation conflict remains a challenge. Emerging AR technologies often exploit focus-tunable optics to address this problem. Although they demonstrated improved depth perception by enabling proper focus cues, a bulky form factor of focus–tunable optics prevents their use in the form of a pair of eyeglasses. Here, we propose a novel optical configuration for a compact vari-focal AR display which deliberately utilizes the zeroth and first diffraction orders of the LC lens to produce two foci: one for a real object and the other for a virtual object with addressable focal planes. The prototype AR glasses can adjust the accommodation distance of the virtual image, mitigating the vergence–accommodation conflict without substantially compromising the form factor or image quality. In addition, we describe the design, fabrication, and characterization of an ultrathin, polarization-insensitive focus-tunable liquid crystal (LC) diffractive lens with a large aperture, a low weight, and a low operating voltage. We show that the polarization dependence of the lens, which is an inherent optical property of LC lenses, can be insensitive using the trilayer birefringent materials and by aligning the optical axes of each birefringent material at a specific angle. The polarization insensitivity eliminates the need for a polarizer, thus further reducing the form factor of the optical system. This novel approach offers significantly reduced complexity for designing AR glasses with addressable focal planes. These technologies for ultrathin lens and AR display show promising potential for developing compact optical systems in various applications.

Single frontal projection autostereoscopic three-dimensional display using a liquid crystal lens array.

Frontal projection autostereoscopic three-dimensional (3D) display is a kind of excellent 3D display technique with large display size and efficient space utilization, especially suitable for the future glasses-free 3D cinema. In this paper, we propose a frontal projection autostereoscopic 3D display using a liquid crystal lens array (LCLA) and a quarter-wave retarding film. The LCLA acts as two roles, refraction and transparency, for different polarized light. The forward projected polarized light can pass through the LCLA as a transparency, and then pass through the quarter-wave retarding film. After reflecting from a polarization-preserving screen, the returned light will pass through the quarter-wave retarding film again and turn to an orthogonal polarization. This polarized light will be refracted by the LCLA and reconstruct the 3D image. The demonstrated LCLA has the merits of no driving voltage, simple fabrication, and cost-effective. Optical experiment verifies the proposed method, which is promising for its potential application in the future glasses-free 3D cinema.

Polarisation-independent liquid crystal lens array with additional dielectric films over self-aligned dual hole-patterned electrodes

ABSTRACT This study demonstrates a type of polarisation-independent liquid crystal (LC) lens arrays that are composed of two orthogonally homogeneous LC layers and self-aligned dual hole-patterned array electrodes. Additional dielectric optical adhesive films coated on patterned electrode surfaces are used to prevent the occurrence of disclination line. The completed LC lens array shows available minimum focal lengths of 12.82 and 13.35 mm at 7 Vrms with respect to individual aluminium (Al) and indium tin oxide (ITO) hole-patterned array electrodes. The LC lens array exhibits the characteristics of electrically tunable focuses, no disclination line, and polarisation-independence.

Properties of AZO film prepared by Sol-Gel in liquid crystal lens with modal control

Properties of AZO film prepared by Sol-Gel in liquid crystal lens with modal control

Simulation of modal control liquid crystal lens with step sheet resistance distribution

Simulation of modal control liquid crystal lens with step sheet resistance distribution

液晶透镜爬山自动对焦算法研究

液晶透镜爬山自动对焦算法研究

GRADIENT ALIGNMENT MATERIALS WITH DIFFERENT PHOTOSENSITIVITY FOR TUNABLE POLARIZATION-INDEPENDENT LIQUID CRYSTAL LENS

The development of electrically tunable liquid crystal (LC) lenses is perspective and promising for a wide range of applications, for example, for imaging system, pico projectors, optical zoom systems, ophthalmology applications and other. Of particular note is the development of polarization-independent LC lenses, as eliminates polarizers from application devices that reduce the efficiency of light transmission through optical systems. Alignment benzaldehyde photosensitive materials, capable of changing the pretilt angles of nematic LC from 90 to 0 ºС in a controlled manner under UV exposure are developed. The anisotropy of the benzaldehyde alignment layers is generated by a two-stage treatment consisting of uniform rubbing with a cloth and subsequent non-polarized UV exposure. Inhomogeneous UV exposure of uniformly rubbed alignment layers allows formation of refractive index gradient inside the LC cell. The concept of tunable polarization-independent self-aligned LC lens based on gradient pretilt angle alignment materials with different photosensitivity is demonstrated. Self-alignment of two polarization-dependent sub-lens is achieved due to a single UV exposure act of two alignment layers, which are located on the same piece of glass on both sides, forming one common optical axis for a polarization-independent LC lens. The independence of the polarization of LC lenses is achieved by setting the azimuthal rubbing direction of the alignment layers of two polarizationdependent LC lenses perpendicular to each other. The sub-lens cells have uniform cell gap and are independently controlled using low-voltage driving. Devices based on gradient benzaldehyde alignment materials can be used in many modern optical and photonic devices.

Influence of SiO2 nanoparticles on electro-optical and thermophysical properties of polyacrylate/liquid crystal composites

ABSTRACTIn this paper, SiO2 nanoparticle-doped polymer dispersed liquid crystal (PDLC) lenses are made from a mixture of prepolymer, 5CB liquid crystal and SiO2 nanoparticles by the polymerisation induced phase separation (PIPS) process. The effect of SiO2 nanoparticles on the electro-optical properties of PDLC films are studied. It is established that SiO2 nanoparticles affect the microstructure of PDLC films significantly because of the formed agglomerates of SiO2 nanoparticles. Results show an improvement in the electro-optical properties and a decrease in the response time for doped systems with small amount of SiO2 nanoparticles. We also observe a shift of nematic–isotropic transition temperature as a function of SiO2 nanoparticle contents. A good agreement between the electro-optical study and thermophysical properties is reached.

Practical Chromatic Aberration Correction in Virtual Reality Displays Enabled by Cost‐Effective Ultra‐Broadband Liquid Crystal Polymer Lenses

AbstractChromatic aberration (CA) is a critical issue in immersive virtual reality displays. The current digital compensation method can reduce the CA by pre‐processing the image contents but at the cost of extra memory space, processing time, and power consumption. Moreover, it is not possible to digitally compensate the CA within each color channel. Here, a practical optical approach is presented to correct the CAs, including the sub‐channel ones, in the virtual reality system, whose functionality is verified by both ray‐tracing analysis and experimental results. In this device, a compact ultra‐broadband Pancharatnam‐Berry phase lens (PBL) with complex axial molecular structure is fabricated and then hybridized with a refractive Fresnel lens. Due to their opposite chromatic dispersion, the system's CA is significantly reduced. To eliminate ghost image from the zero‐order leakage of PBL, a broadband circular polarizer is implemented to block the stray light. As a result, clear image within the entire 100° field‐of‐view is achieved. The proposed large‐size cost‐efficient broadband wide‐view flat optics can practically benefit not only virtual reality displays but also general imaging systems for practical applications and scientific research.

Electrically tunable gradient-index lenses via nematic liquid crystals with a method of spatially extended phase distribution.

The dilemma between tunable range of a lens power and an aperture size in gradient-index (GRIN) type of liquid crystal (LC) lenses is well known due to the limitation of birefringence of LC martials and the nature of soft matters. In order to overcome the dilemma of the power law, a multi-layered LC lens was previously proposed by us. However, the aperture size of GRIN LC lenses is still difficult to exceed 10 mm. In this paper, we proposed an electrically tunable GRIN LC lens via nematic liquid crystals with a method of spatially extended phase distribution. A GRIN LC lens with an aperture size of 20 mm is achieved. The proposed GRIN LC lens consists of two LC elements modulating wavefronts at different regions of the lens aperture extending to 20 mm. The lens power of the GRIN LC lens is continuously tunable, while the LC lens can function as a positive lens, a negative lens, and a bifocal lens. The proposed GRIN LC lens not only overcomes the dilemma of the power law but also provides a more practical approach that could benefit the ophthalmic applications and augmented reality systems.

Improvement of Hole-Patterned Electrode Liquid Crystal Lens by Coplanar Inner Ring Electrode

In this study, the electro-optical performance of coplanar inner floating ring (CIFR)–hole-patterned electrode (with 1 mm aperture size) liquid crystal (LC) lens (HPELCL) was examined. Various experimental conditions, such as driving frequencies and cell structures, affecting the performance of the proposed lenses were analyzed and discussed via an electric circuit model. The CIFR electrodes successfully reduced the applied voltages with low driving frequencies and provided a larger lens power than conventional HPELCL. The floating ring electrode generated an induced electric field to contribute to the original fringe electric field by the hole-patterned electrode. The combined electric field yielded additional LC reorientations to achieve the same lens performance with decreased electric voltages. The proposed LC lens exhibited easy fabrication, tunable focuses, free of disclination line, and low power consumption. The experimental results were illustrated with the electric circuit model.

Adaptive nematic liquid crystal lens array with resistive layer

ABSTRACTWe propose an adaptive nematic liquid crystal (LC) lens array using a dielectric layer with low dielectric constant as resistive layer. With the resistive layer and periodic-arranged iridium tin oxide (ITO) electrodes, the vertical electric field across the LC layer varies linearly over the lens aperture is obtained in the voltage-on state. As a result, a centrosymmetric gradient refractive index profile within the LC layer is generated, which causes the focusing behaviour. As a result of the optimisation, a thin cell gap which greatly reduces the switching time of the LC lens array can be achieved in our design. The main advantages of the proposed LC lens array are in the comparatively low operating voltage, the flat substrate surface, the simple electrodes, and the uniform LC cell gap. The simulation results show that the focal length of the LC lens array can be tuned continuously from infinity to 3.99 mm by changing the applied voltage.

P‐11.6: A blue phase liquid crystal lens with large tunable focal length range using different birefringence materials

P‐11.6: A blue phase liquid crystal lens with large tunable focal length range using different birefringence materials

Holographic display technology based on liquid crystal device

AbstractHolographic display technology can reconstruct the same images of the original objects exactly, which has played a more and more important role and become the goal of the three‐dimensional display. As liquid crystal devices can modulate the polarization state of light, they have been widely used in the holographic display to modulate the phase and amplitude of information. Among them, liquid crystal spatial light modulator and liquid crystal lens are two important devices in the holographic diffraction. In this paper, several liquid crystal devices have been introduced and the holographic display technologies based on these liquid crystal devices have been discussed. The merits and demerits of these technologies based on the liquid crystal devices have been analyzed, and the outlook of the holographic display is given in the end.

Electrically Tunable-Focusing Liquid Crystal Microlens Array with Simple Electrode

An electrically tunable-focusing liquid crystal (LC) microlens array exhibiting a wide-range tunable focal length is proposed. The lower substrate has strip indium tin oxide (ITO) electrodes, the upper substrate has periodic ITO electrodes with a certain gap coated on the inner surface., and an LC microlens is generated between the two strip electrodes. For each LC microlens, the gap between the top planar electrodes is directly above the center of the microlens. Unlike the conventional LC lens, the individual LC microlens is not coated with ITO electrodes on the central part of its upper and lower substrates, which helps to maintain the LC’s horizontal orientation. In the voltage-off state, the focal length of the microlens array is infinity because of the homogeneous LC alignment. At a given operating voltage, an ideal gradient refractive index distribution is induced over the homogeneous LC layer, which leads to the focusing effect. The simulation result shows that the focal length of the LC microlens could be gradually drawn to 0.381 mm with a change of voltage.

Double-layer liquid crystal lens array with composited dielectric layer

ABSTRACT A double-layer liquid crystal (LC) lens array with composited dielectric layer is proposed. In our design, a spatially non-uniform electric field is generated between the strip electrodes, resulting in a gradient refractive index distribution in the LC layer. Since the upper and lower parts of the LC lens array both adopt a composite dielectric layer, the operation voltage of the LC lens array is effectively reduced. In terms of LC lenslet, the double-layer design doubles the phase difference between the centre and the periphery of the LC layer, thereby reducing the focal length of the LC lens array. In addition, the shortest focal length (~1.78 mm) of the LC lens array is obtained at V = 3.3 V, and the LC lens array has a large focusing range.

An optical system for augmented reality with electrically tunable optical zoom function and image registration exploiting liquid crystal lenses.

An optical-see-through augmented reality (AR) system assists our daily work by augmenting our sense with computer-generated information. Two of optical challenges of AR are image registration and vision correction due to fixed optical properties of the optical elements of AR systems. In this paper, we demonstrated an AR system with optical zoom function as well as a function of image registration via two LC lenses in order to help people see better by magnifying the virtual image and adjusting the location of virtual image. The operating principles are introduced, and experiments are performed. The concept demonstrated in this paper could be further extended to other electro-optical devices as long as the devices exhibit the capability of phase modulations.