【摘要】 液晶透镜在高频电压的驱动下，基板间的电容会导致透镜相位分布偏离理想的抛物线分布，影响其性能。为解决这一问题，提出一种分段式液晶菲涅耳透镜电极结构的设计方法，该设计能有效增大液晶菲涅耳透镜驱动电压频率适用范围。实验结果表明：分四段的液晶菲涅耳透镜相较于传统的液晶菲涅耳透镜，其截止频率提高至16倍。该结构为实现大口径快速响应液晶透镜提供重要依据。更多还原

【Abstract】 Objective Liquid crystal lenses have garnered significant attention due to their unique properties, such as electrically tunable focal length, compact size, and the absence of mechanical moving parts. These features make them highly suitable for various applications, including vision correction, 2D/3D display switching, and light field displays. However, the performance of liquid crystal lenses is significantly influenced by the capacitive effects that arise from the inter-substrate capacitance, particularly when driven by high-frequency voltages. This capacitive effect causes the phase distribution of the lens to deviate from the ideal parabolic profile, thereby degrading its optical performance. The primary objective of this study is to address this limitation by proposing an innovative segmented-electrode architecture for liquid crystal Fresnel lenses. This design aims to extend the operational frequency range of the driving voltages, thereby enhancing the lens’ s performance and applicability in high-frequency scenarios.Methods We begin with a theoretical analysis of the relationship between the driving voltage cutoff frequency and the structural parameters of the lens. The liquid crystal Fresnel lens is modeled as a series of concentric rings, each with a specific radius and capacitance. The phase distribution of each ring is designed to be parabolic, ensuring that the overall phase distribution forms a continuous and smooth parabolic profile. However, the presence of resistive electrodes causes the voltage distribution across the rings to deviate from the ideal parabolic shape, leading to a multi-focus lens effect. To mitigate this issue, metal electrode lines are introduced at the boundaries of each Fresnel zone and the input electrode to ensure consistent optical power across each zone. The lens structure is then segmented into multiple independent regions, each driven by a separate voltage source. This segmentation reduces the length of each concentric ring, thereby increasing the cutoff frequency. The theoretical model is supported by experimental validation, where the proposed segmentedelectrode structure is fabricated and tested against a traditional liquid crystal Fresnel lens. The fabrication process involves several steps, including cleaning the substrates, applying polyimide alignment layers, rubbing the substrates to induce alignment, and assembling the liquid crystal cell. The liquid crystal material used in this study is HTW148700-100, which exhibits a linear response within a specific voltage range. The electrodes are connected to a driving circuit that supplies square wave signals at varying frequencies. Interferometric techniques are employed to measure the wavefront distortion caused by the capacitive effects at different driving frequencies.Results and Discussions The experimental results demonstrate that the segmented-electrode structure significantly enhances the high-frequency performance of the liquid crystal Fresnel lens. The traditional lens exhibits a marked deviation from the ideal parabolic phase distribution at relatively low frequencies, leading to distorted wavefronts. In contrast, the segmented lens maintains a smooth parabolic phase distribution up to a much higher frequency, as evidenced by the interferometric measurements. Fig.7 illustrates the wavefront curves of the traditional liquid crystal Fresnel lens. At frequencies below the cutoff frequency, the wavefront is smooth and parabolic, indicating minimal capacitive effects. However, as the frequency increases beyond the cutoff frequency, the wavefront becomes distorted, with the phase distribution deviating from the ideal parabolic shape. This distortion is attributed to the increased capacitive reactance, which causes a significant voltage drop across the electrodes. In contrast, Fig.9 shows the wavefront curves of the segmented liquid crystal Fresnel lens. The segmented design effectively mitigates the capacitive effects, allowing the lens to maintain a smooth parabolic wavefront up to a frequency of 15000 Hz. This represents a sixteen-fold increase in the cutoff frequency compared to the traditional design, thereby validating the theoretical predictions. The imaging performance of the lenses is also evaluated using an ISO 12233 resolution chart. The results indicate that the segmented lens provides superior imaging quality at high frequencies, with clearer and more distinct patterns compared to the traditional lens. The response time of the segmented lens is measured to be approximately 0.75 s for switching from the off state to the on state and 0.43 s for the reverse transition. The response time is competitive with other high-performance liquid crystal devices.Conclusions We highlight the significant impact of capacitive effects on the performance of liquid crystal Fresnel lenses, particularly at high driving frequencies. The proposed segmented-electrode architecture effectively mitigates these effects, thereby extending the operational frequency range of the lens. The experimental results demonstrate a sixteen-fold increase in the cutoff frequency compared to traditional designs, making the segmented lens suitable for high-frequency applications. The segmented design not only enhances the high-frequency performance but also maintains a compact lens thickness and rapid response time. The use of metal electrode lines at the Fresnel zone boundaries ensures consistent optical power across each zone, thereby preserving the lens’ s imaging quality. This design provides a crucial technical foundation for the development of large-aperture and fast-response liquid crystal lenses, with potential applications in advanced optical systems and imaging technologies. In conclusion, we underscore the importance of addressing capacitive effects in the design of high-frequency liquid crystal lenses. The segmented-electrode structure offers a practical solution to this challenge, paving the way for future innovations in liquid crystal lens technology.更多还原