Virtual reality(VR)is regarded as the next-generation display platform for immersive human-computer interaction.To solve the long-existing problem of vergence accommodation conflict in VR,varifocal displays based on t...Virtual reality(VR)is regarded as the next-generation display platform for immersive human-computer interaction.To solve the long-existing problem of vergence accommodation conflict in VR,varifocal displays based on the diffractive Pancharatnam–Berry lens(PBL)are considered as one of the most promising approaches with great compatibility to current display architectures.However,the diffractive nature of PBL leads to serious chromatic aberrations in optical systems,which deteriorates the image quality and discourages its actual usage.展开更多
A compound varifocal lens based on electromagnetic drive technology is designed and fabricated, where the polydimethylsiloxane(PDMS) film acts as a driving component, while the PDMS biconvex lens and the plane-concave...A compound varifocal lens based on electromagnetic drive technology is designed and fabricated, where the polydimethylsiloxane(PDMS) film acts as a driving component, while the PDMS biconvex lens and the plane-concave lens form a coaxial compound lens system. The plane-concave lens equipped with driving coils is installed directly above the PDMS lens surrounded by the annular magnet. When different currents are applied, the annular magnet moves up and down, driving the PDMS film to undergo elastic deformation, and then resulting in longitudinal movement of the PDMS lens. The position change of the PDMS lens changes the focal length of the compound lens system. To verify the feasibility and practicability of this design, a prototype of our compound lens system is fabricated in experiment. Our proposed compound lens shows that its zoom ability reaches 9.28 mm when the current ranges from -0.20 A to 0.21 A.展开更多
Augmented reality(AR)displays have gained significant attention for their ability to blend the real and virtual worlds seamlessly.However,they face challenges like the vergence-accommodation conflict and a limited eye...Augmented reality(AR)displays have gained significant attention for their ability to blend the real and virtual worlds seamlessly.However,they face challenges like the vergence-accommodation conflict and a limited eyebox.The AR community is actively seeking lightweight,integrative optical elements to overcome these limitations.In this study,we demonstrate a three-dimensional varifocal meta-device for AR display.The meta-device is composed of three cascaded metasurfaces with Moiréand off-center Fresnel lens phase profiles designed to dynamically manipulate the focus point in three-dimensional space.The cascaded metasurfaces are designed and fabricated by the TiO_(2)nanopillars with varying diameters,which are polarizationinsensitive for light field manipulation.The focal point position is precisely controlled by the relative rotation between the metasurfaces.The meta-device achieves an effective focal length ranging from 3.7 mm to 33.2 mm and can adjust the lateral focal point within the same range.The dynamic eyebox size varies from 4.2 mm to 5.8 mm.This lightweight,integrated meta-device is well-suited for various imaging applications,including AR displays,as it simultaneously addresses the vergence-accommodation conflict and expands the eyebox.展开更多
This study proposes compact Alvarez varifocal lenses with a wide varifocal range,which consist of a set of Alvarez lenses and three sets of ordinary lenses.The Alvarez lenses have a double freeform surface and are dri...This study proposes compact Alvarez varifocal lenses with a wide varifocal range,which consist of a set of Alvarez lenses and three sets of ordinary lenses.The Alvarez lenses have a double freeform surface and are driven by a cam-driven structure.The axial size of the proposed varifocal Alvarez lenses is only 30.50 mm.The experimental results show that the proposed varifocal lens can achieve a focal length range from 15 to 75 mm,and the imaging quality is still in an acceptable range for optical lens requirements.The compact varifocal Alvarez lenses are expected to be used in surveillance systems,industrial inspection,and machine vision.展开更多
针对无人机航拍时拍摄的对象大小不一、种类繁杂且容易被建筑遮挡等问题,提出了一种基于YOLOv5s的无人机目标检测改进算法VA-YOLO。在已有的主干网络中添加CA注意力机制模块,扩大检测区域,获得更准确的位置信息;针对检测小目标时尺度不...针对无人机航拍时拍摄的对象大小不一、种类繁杂且容易被建筑遮挡等问题,提出了一种基于YOLOv5s的无人机目标检测改进算法VA-YOLO。在已有的主干网络中添加CA注意力机制模块,扩大检测区域,获得更准确的位置信息;针对检测小目标时尺度不一导致语义丢失的问题,添加小目标检测层与BiFPN结构,加深浅层语义与深层语义结合,以此丰富对检测目标的语义信息;使用损失函数Varifocal loss与EIoU,改善模型对小目标检测的准确性。实验结果表明,在VisDrone2019-DET数据集上,该算法的平均检测精度(mean Average Precision,mAP)达到了39.01%,相比YOLOv5s提高了6.26%。展开更多
基金National Natural Science Foundation of China(62405021,U24A20304)Beijing Nova Program(20240484557)。
文摘Virtual reality(VR)is regarded as the next-generation display platform for immersive human-computer interaction.To solve the long-existing problem of vergence accommodation conflict in VR,varifocal displays based on the diffractive Pancharatnam–Berry lens(PBL)are considered as one of the most promising approaches with great compatibility to current display architectures.However,the diffractive nature of PBL leads to serious chromatic aberrations in optical systems,which deteriorates the image quality and discourages its actual usage.
文摘A compound varifocal lens based on electromagnetic drive technology is designed and fabricated, where the polydimethylsiloxane(PDMS) film acts as a driving component, while the PDMS biconvex lens and the plane-concave lens form a coaxial compound lens system. The plane-concave lens equipped with driving coils is installed directly above the PDMS lens surrounded by the annular magnet. When different currents are applied, the annular magnet moves up and down, driving the PDMS film to undergo elastic deformation, and then resulting in longitudinal movement of the PDMS lens. The position change of the PDMS lens changes the focal length of the compound lens system. To verify the feasibility and practicability of this design, a prototype of our compound lens system is fabricated in experiment. Our proposed compound lens shows that its zoom ability reaches 9.28 mm when the current ranges from -0.20 A to 0.21 A.
基金The National Key R&D Program of China(Grant Nos.2022YFA1404700)the Major Key Project of PCL(PCL2024A01)+7 种基金Shenzhen Municipal Basic Research(Key Project)(JCY20241202123919027)the National Natural Science Foundation of China(Nos.62305184)Basic and Applied Basic Research Foundation of Guangdong Province(2023A1515012932)Science,Technology and Innovation Commission of Shenzhen Municipality(WDZC20220818100259004)the Research Grants Council of the Hong Kong Special Administrative Region,China[Project No.C5031-22GCityU11310522CityU11300123]City University of Hong Kong[Project No.9610628].
文摘Augmented reality(AR)displays have gained significant attention for their ability to blend the real and virtual worlds seamlessly.However,they face challenges like the vergence-accommodation conflict and a limited eyebox.The AR community is actively seeking lightweight,integrative optical elements to overcome these limitations.In this study,we demonstrate a three-dimensional varifocal meta-device for AR display.The meta-device is composed of three cascaded metasurfaces with Moiréand off-center Fresnel lens phase profiles designed to dynamically manipulate the focus point in three-dimensional space.The cascaded metasurfaces are designed and fabricated by the TiO_(2)nanopillars with varying diameters,which are polarizationinsensitive for light field manipulation.The focal point position is precisely controlled by the relative rotation between the metasurfaces.The meta-device achieves an effective focal length ranging from 3.7 mm to 33.2 mm and can adjust the lateral focal point within the same range.The dynamic eyebox size varies from 4.2 mm to 5.8 mm.This lightweight,integrated meta-device is well-suited for various imaging applications,including AR displays,as it simultaneously addresses the vergence-accommodation conflict and expands the eyebox.
基金supported by the National Natural Science Foundation of China(No.62275017)the Preliminary Study(No.202303042)the National Key Research and Development Program of China(No.2024YFC2207004)。
文摘This study proposes compact Alvarez varifocal lenses with a wide varifocal range,which consist of a set of Alvarez lenses and three sets of ordinary lenses.The Alvarez lenses have a double freeform surface and are driven by a cam-driven structure.The axial size of the proposed varifocal Alvarez lenses is only 30.50 mm.The experimental results show that the proposed varifocal lens can achieve a focal length range from 15 to 75 mm,and the imaging quality is still in an acceptable range for optical lens requirements.The compact varifocal Alvarez lenses are expected to be used in surveillance systems,industrial inspection,and machine vision.
文摘针对无人机航拍时拍摄的对象大小不一、种类繁杂且容易被建筑遮挡等问题,提出了一种基于YOLOv5s的无人机目标检测改进算法VA-YOLO。在已有的主干网络中添加CA注意力机制模块,扩大检测区域,获得更准确的位置信息;针对检测小目标时尺度不一导致语义丢失的问题,添加小目标检测层与BiFPN结构,加深浅层语义与深层语义结合,以此丰富对检测目标的语义信息;使用损失函数Varifocal loss与EIoU,改善模型对小目标检测的准确性。实验结果表明,在VisDrone2019-DET数据集上,该算法的平均检测精度(mean Average Precision,mAP)达到了39.01%,相比YOLOv5s提高了6.26%。
