Liquid Crystal Lens Array Research Articles

Towards a mini-endoscope design with spatially selective excitation and imaging.

We describe a mini-endoscope design that uses a new type of electrically tunable liquid crystal lens array enabling the dynamic increase of spatial resolution by adjusting the working distance in various zones of interest over a relatively large field of view (FoV) without mechanical movement. The characterization of the system is performed by using uniform fluorescent films, fluorescent micro spheres and a tissue sample expressing the fluorescent calcium indicator GCaMP6s. Lateral resolution of up to 2 µm over the FoV between 300 µm - 400 µm is experimentally demonstrated.

Large aperture liquid crystal lens array based on integrated composite electrodes for 2D/3D switchable displays

A large aperture liquid crystal (LC) lens array based on integrated composite electrodes (ICE-LC) lens array with low operating voltages is proposed. The top substrate contains composite electrodes, while the bottom substrate contains strip electrodes. Composite electrodes are further categorized into integral plate electrode (IPE) and rectilinear-patterned electrode (RPE). Meanwhile, the strip electrodes consist of auxiliary electrodes and pixel electrodes. During the focusing mode, the electric field can easily propagate through the LC layer. Simultaneously, the voltage on auxiliary electrodes is maintained lower than that on pixel electrodes to optimize the electric field distribution. To assess the operating efficiency of the ICE-LC, an evaluation of the conventional model is taken during the simulation. Simulation results show that the ICE-LC lens array achieves the shortest focal length at a low operating voltage. The pixel electrodes operate at 4.5 Vrms, and the auxiliary electrodes at 0.9 Vrms. This configuration provides an ideal refractive index profile in a relatively thick LC layer. Additionally, this configuration enables 2D/3D switchable display, outperforming current LC lens array in the equivalent aperture.

Liquid crystal lens array based on polymer protrusion

Liquid crystal lens array based on polymer protrusion

P‐12.9: A Switchable Liquid Crystal Microlens Between 1D and 2D Arrays

P‐12.9: A Switchable Liquid Crystal Microlens Between 1D and 2D Arrays

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 (∼6.5Vrms), 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 lens array with positive and negative focal lengths.

A positive-negative tunable liquid crystal lens array is proposed by electrode design. The electrode structure consists of two main units, one of them is used to generate parabolic voltage profile and the other one distributes the voltage homogeneously across the lens aperture. The proposal features the advantages of high-quality performance, simple fabrication process (a single lithographic step), compact design, low voltages and simple driving method. In addition, the lens array can be driven as a square lens array or a rotatable cylindrical lens array. The voltage difference between the electrodes on the inner face of two substrates is controlled within the range that the phase of liquid crystal layer responds linearly to voltage difference, then the phase of the lens array maintains parabolic profile in the whole focus range. In experiments, a lens array with 30 µm liquid crystal layer is fabricated using the designed electrode. The size of the array area is 11 × 11 mm, and the side length of an individual square lens is 1.0 mm. The results show that the phase profile matches with the parabolic profile during focus tuning, and good focusing effect of the positive lens is observed. As a result, a liquid crystal lens array with high-quality performance is experimentally demonstrated, and the experimental results are consistent with the theoretical analyses.

Switchable 2D/3D display based on a liquid crystal lens array and the rotating specimen shooting method.

A liquid crystal (LC) lenticular lens array with auxiliary electrodes is proposed. The introduction of the auxiliary electrodes helps to obtain an LC lens array (LCLA) with relatively large aperture without complex structures. When the LCLA is in the focusing state, the voltage of auxiliary electrodes is less than that of edge electrodes, and the generated electric field in the LCLA can penetrate into the LC layer. Therefore, the ideal phase profile is obtained with a relatively thin LC layer thickness. Experimental results show that the LCLA has the characteristics of high optical power and low operation voltage. Based on the proposed LCLA, a multi-view 2D/3D switchable display is realized. In the experiment, a series of parallax images is obtained by rotating the sample to replace the convergence shooting method for 3D imaging. Compared with other 2D/3D switchable display devices, the multi-view 2D/3D switchable display based on the LCLA is characterized by being thin and compact, and displaying no moiré pattern.

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 (5Vrms). 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.

Polymer Stabilized Paraboloid Liquid Crystal Microlenses with Integrated Pancharatnam–Berry Phase

AbstractAspheric lenses reduce aberration and provide sharper images with improved spot size compared to spherical lenses. This paper demonstrates that applying shear flow can produce plano‐concave liquid crystal (LC) lens arrays with paraboloid aspheric profiles. The focal length of individual lenses, with a 0.2 mm aperture, decreases from 0.67 to 0.45 mm as the chiral dopant increases from 0 to 6 wt%. The focal length is also sensitive to the polarization state of the incoming light. The lenses are stabilized by photopolymerizing with 6 wt% of reactive monomer added to the LC. A qualitative explanation for the flow‐induced lens formation and the optical properties of the lenses is provided. The potential tunability of the lenses in various fields and their use as paraboloid reflectors are discussed.

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.

Wide‐view augmented reality display with diffractive cholesteric liquid crystal lens array

AbstractA novel augmented reality display is proposed to achieve a field of view of 100°, while maintaining a good form factor with a glass‐thin waveguide combiner. The out‐coupler consists of an array of off‐axis diffractive lenslets with extremely low f‐number. A breadboard system is built and its performance characterized, combined with analysis and discussion of further improvement.

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.

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.

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.

P‐91: Tunable Blue Phase Liquid Crystal Lens Array Using Composite Dielectric Layer

We demonstrate a tunable focus and polarization‐independent blue‐phase liquid crystal lens array using a composite dielectric layer. With strip electrodes and a planar top electrode, gradient electric fields are generated. As the applied voltage is varied, the focal length of the lens can be continuously tuned from ∞ to 14 mm.

Application of Dimming Compensation Technology Via Liquid Crystal Lens for Non-Imaging Projection Laser Systems

The main purpose of this paper is to explore a newly developed optical design, then to further improve the overhead lighting contrast in the laser projector module. In terms of the structural design of the projector, a liquid crystal lens array was used as the local dimming system for the light source, in order to achieve the objective, which was to significantly improve the contrast facility of the projection system. Second, in terms of the design of the light source, the output method for the light source was a laser light source employing arrays of micro-scanning. The main purpose was to compensate for the dim spots in the hole between the lenses in each unit of the liquid crystal when the liquid crystal lens array was locally dimmed, and thus significantly improving the contrast facility of the projection system. In terms of the software simulation, a liquid crystal lens array was used to simulate a pore size of 2.0 mm and focal lengths of 9 cm and 23 cm. The end effect gave good control and adjustment of the bright and dark areas during local dimming of the projector’s imaging chip components. For a single laser source, the maximum contrast for local dimming was about 128:1, 438:1, and 244:1, for the Red (R), Green (G), and Blue (B) optical paths, respectively. The light efficiency scores were approximately 20.91%, 20.05%, and 24.45%, for the R, G, and B optical paths, respectively. After compensation using a micro-scanning light source, the defect of having dim spots between the pores was remedied, and the light adjustment area became more uniform while the contrasts became smaller. The maximum contrasts were approximately 52:1, 122:1, and 110:1, for the R, G, and B optical paths, respectively. For the projector, when the liquid crystal lenses were not transmissive, the maximum uniformity scores were 82.25%, 87.15%, and 88.43%, for the R, G, and B optical paths, respectively.

A blue-phase liquid crystal lens array based on dual square ring-patterned electrodes

ABSTRACTWe propose a blue-phase liquid crystal (BPLC) lens array based on dual square ring-patterned electrodes. A high dielectric constant layer is used to smoothen out the horizontal electric field and reduce the operating voltage. By creating a potential difference between the dual square ring-patterned electrodes, gradient electric fields are generated and lens-like phase profile is obtained. Besides, the focal length of the BPLC lens is adjustable with voltage changes and all simulation results indicate that the BPLC lens array is polarisation-insensitive.

P‐149: A Polarization‐independent Blue Phase Liquid Crystal Lens Array with Multi‐electrode

A polarization‐independent blue‐phase liquid crystal lens array using multi‐electrodes is proposed. A high dielectric constant layer helps to smoothen out the horizontal electric field and reduce the operating voltage. With multi‐electrodes and a planar top electrode, the gradient electric fields are generated, and the lens‐like phase profile is obtained. When the applied voltage is changed, the focal length of the lens can be tuned from ∞ to 6.7 mm. Besides, the simulation results show that the lens is insensitive to polarization while keeping parabolic‐like profile.