Ming-Syuan Chen

A Review of Electrically Tunable Focusing Liquid Crystal Lenses

Electrically tunable focusing liquid crystal (LC) lenses are reviewed in this paper. The distribution of the orientations of LC directors which is controlled by electric fields results in a distribution of refractive indices of LC directors. The incident light can be modulated by the electrically tunable lens-like phase difference of the LC lens. We introduce the basic operating principles of LC lenses and discuss the structures of LC lenses. The major challenges of LC lenses are also discussed. We believe this paper provides a guideline for basic understanding of LC lenses.

An electrically tunable optical zoom system using two composite liquid crystal lenses with a large zoom ratio

An electrically tunable-focusing optical zoom system using two composite LC lenses with a large zoom ratio is demonstrated. The optical principle is investigated. To enhance the electrically tunable focusing range of the negative lens power of the LC lens for a large zoom ratio, we adopted two composite LC lenses. Each composite LC lens consists of a sub-LC lens and a planar polymeric lens. The zoom ratio of the optical zooming system reaches ~7.9:1 and the object can be zoomed in or zoomed out continuously at the objective distance of infinity to 10 cm. The potential applications are cell phones, cameras, telescope and pico projectors.

A holographic projection system with an electrically tuning and continuously adjustable optical zoom

A holographic projection system with optical zoom is demonstrated. By using a combination of a LC lens and an encoded Fresnel lens on the LCoS panel, we can control zoom in a holographic projector. The magnification can be electrically adjusted by tuning the focal length of the combination of the two lenses. The zoom ratio of the holographic projection system can reach 3.7:1 with continuous zoom function. The optical zoom function can decrease the complexity of the holographic projection system.

A Pico Projection System With Electrically Tunable Optical Zoom Ratio Adopting Two Liquid Crystal Lenses

A pico projection system with electrically tunable optical zoom ratio adopting two liquid crystal (LC) lenses is first demonstrated. The projected image of the system is not only continuously focused, but also zoomed simultaneously by adjusting the focal lengths of LC lenses electrically. The related optical principle is discussed and a liquid-crystal-on-silicon (LCOS)-based pico projection system was used to demonstrate the designed concept. This study opens a new window in realizing pico projectors with electrically tunable optical zooms.

An electrically tunable imaging system with separable focus and zoom functions using composite liquid crystal lenses

We demonstrated an electrically tunable optical image system with separable focus function and zoom function based on three tunable focusing composite liquid crystal (LC) lenses. One LC lens in charge of the focus function helps to maintain the formed image at the same position and the other two LC lenses in charge of zoom function assist to continuously form an image at image sensor with tunable magnification of image size. The detail optical mechanism is investigated and the concept is demonstrated experimentally. The magnifications of the images can be switched continuously for the target in a range between 10 cm and 100 cm. The optical zoom ratio of this system maintains a constant~6.5:1 independent of the object distance. This study provides not only a guideline to design the image system with an electrically optical zoom, but also provide an experimental process to show how to operate the tunable focusing lenses in such an image system.

A polarization-independent liquid crystal phase modulation using polymer-network liquid crystals in a 90° twisted cell

A polarization-independent liquid crystal phase modulation using polymer-network liquid crystals in a 90° twisted cell (T-PNLC) is demonstrated. T-PNLC consists of three layers. Liquid crystal (LC) directors in the two layers near glass substrates are orthogonal to each other and those two layers modulate two eigen-polarizations of an incident light. As a result, two eigen-polarizations of an incident light experience the same phase shift. In the middle layer, LC directors are perpendicular to the glass substrate and contribute no phase shift. The phase shift of T-PNLC is electrically tunable and polarization-independent. T-PNLC does not require any bias voltage for operation. The phase shift is 0.28 π rad for the voltage of 30 Vrms. By measuring and analyzing the optical phase shift of T-PNLC at the oblique incidence of transverse magnetic wave, the pretilt angle of LC directors and the effective thickness of three layers are obtained and discussed. The potential applications are spatial light modulators...

A Holographic Projection System With an Electrically Adjustable Optical Zoom and a Fixed Location of Zeroth-Order Diffraction

An electrically tunable optical zooming holographic projection system with a fixed location of zeroth-order diffraction is demonstrated. By using two liquid lenses and an encoded Fresnel lens on a liquid crystal on silicon (LCoS) panel, the size of the projected image of the holographic projection system is changeable; meanwhile, the locations of both of the zeroth-order diffraction and the first-order diffraction are unchanged. Therefore, the zeroth-order diffraction can be removed by using a fixed optical high-pass filter. We can use it to realize an image size matching system for green light (532 nm) and red light (632.8 nm) without any positional motion of the optical elements. The optical zoom function enhances the feasibility to realize a high-resolution full-color holographic projection system.

An Electrically Tunable Focusing Pico Projector Using a Liquid Crystal Lens as an Active Optical Element

An electrically tunable pico projector adapting a liquid crystal (LC) lens as an active optical element is demonstrated. The electrically tunable focusing properties of the pico-projectors with different aperture sizes of the LC lenses are also investigated. The tunable ranges of the electrically tunable pico projectors are 350 cm to ∼14 cm. The response times are 1.2 sec for the LC lens of 2 mm aperture and around 5 sec for the LC lens of 4 mm aperture. The image performance of the electrically tunable focusing pico projector is demonstrated.

Electrically Tunable Ophthalmic Lenses for Myopia and Presbyopia Using Liquid Crystals

In this paper, an electrically tunable-focusing and polarizer-free liquid crystal (LC) lens for ophthalmic lenses is demonstrated. The optical operating principles of the LC lens in a human eye system are introduced and the optical principle of the polarization independent of the double-layered LC lens is investigated. The polarization dependency, image quality and the response time of the double-layered LC lens are measured. The continuously tunable-focusing properties of the LC lenses are more practical in applications for different visional conditions of people. The concept in this paper can also be extensively applied to imaging systems, and projection systems, such as cameras in cell phones, pico projectors, and endoscopes.

Electrically Tunable Liquid Crystal Lenses and Applications

Electrically tunable liquid crystal (LC) lenses have been studied for over 30 years. Three main problems of LC lenses hinder the applications: 1) the paradox between the response time and tunable focusing range, 2) polarization dependency, and 3) large aperture size for ophthalmic lenses. In this paper, we introduce the two mode switching method of the LC lenses to solve the paradox of the LC lenses. The basic optical principles for designing polarization independent LC lenses are discussed and several polarizer-free LC lenses we developed are reviewed. Several applications of LC lenses are also introduced, including auto-focusing imaging systems, auto-focusing projection systems, optical zoom systems, endoscopic systems, solar cells, ophthalmic lenses for myopia-presbyopia.