Integrating optical design with Taguchi method in a remote wireless light charging system

Abstract

Power cannot be efficiently transmitted over long distances using conventional wireless transmission. Although increasing charger power effectively improves charging efficiency, safety concerns include mobile phone heating, long-term health damage caused by electromagnetic waves, and interferences on other precise instruments. This study proposed a remote wireless charging system that utilizes mechanical movement design in zoom lenses to maintain wireless charging system performance and perform charging operations from different positions in a room through the movement between lens groups. Moreover, the Taguchi method was applied in optical design software to identify the optimal factors for performance improvement. The wireless light charging system was optimized using the Taguchi method. In addition, optimization of curvature, thickness, and material were proposed. Three focal lengths were optimized through 18 sets of experimental data to reduce the spherical and comatic aberrations; and modulation transfer function value was improved to enhance the performance of the remote wireless light charging system. The remote wireless light charging system was designed to be used in an indoor space. In general, the system is installed on the ceiling, and mechanical movement function is enabled for the lens. Moving the lens changes the focus of the system. This allows the charging light source to change its original light path and generate a new focal point. The system features three zoom positions: 3 m from the ceiling to the floor, 2 m from the ceiling to the desktop, and 1.5 m from the ceiling to a person standing with a mobile phone. This allows the wireless light charging system to focus on the mobile phone receiver for charging in every corner within the indoor space. The wireless charging system features three focal lengths; the field of view (FOV) values are 0°, 24°, and 34°; the total length of the system is 635.45 mm; and the size of the spot diagram is < 12.96 mm. Testing the system revealed that in terms of ${\text{F}} - \theta$, the control was < ±5%; the performance of the relative illumination was more than 90%, the modulation transfer function reached > 20% at various FOV angles at a spatial frequency of 80 lp/mm; and the lateral color was  < ± 2 μm. A photodiode with an area of 12.0 mm was used as the receiver, and energy could be effectively received when the spot size was greater than or equal to the receiving area.