Current freeform illumination optical designs are mostly focused on producing prescribed irradiance distributions on planar targets.Here,we aim to design freeform optics that could generate a desired illumination on a...Current freeform illumination optical designs are mostly focused on producing prescribed irradiance distributions on planar targets.Here,we aim to design freeform optics that could generate a desired illumination on a curved target from a point source,which is still a challenge.We reduce the difficulties that arise from the curved target by involving its varying z-coordinates in the iterative wavefront tailoring(IWT)procedure.The new IWT-based method is developed under the stereographic coordinate system with a special mesh transformation of the source domain,which is suitable for light sources with light emissions in semi space such as LED sources.The first example demonstrates that a rectangular flat-top illumination can be generated on an undulating surface by a spherical-freeform lens for a Lambertian source.The second example shows that our method is also applicable for producing a non-uniform irradiance distribution in a circular region of the undulating surface.展开更多
The development of color routers(CRs)realizes the splitting of dichromatic components,contributing to the modulation of photon momentum that acts as the information carrier for optical information technology on the fr...The development of color routers(CRs)realizes the splitting of dichromatic components,contributing to the modulation of photon momentum that acts as the information carrier for optical information technology on the frequency and spatial domains.However,CRs with optical stimulation lack active control of photon momentum at deep subwavelength scale because of the optical diffraction limit.Here,we experimentally demonstrate an active manipulation of dichromatic photon momentum at a deep subwavelength scale via electron-induced CRs,where the CRs radiation patterns are manipulated by steering the electron impact position within 60 nm in a single nanoantenna unit.Moreover,an encrypted display device based on programmable modulation of the CR array is designed and implemented.This approach with enhanced security,large information capacity,and high-level integration at a deep subwavelength scale may find applications in photonic devices and emerging areas in quantum information technologies.展开更多
Compactness and light weight,large exit pupil diameter and distance,small distortion for virtual image,and see-through light paths are pivotal factors to achieve a better,wearable experience of optical see-through hea...Compactness and light weight,large exit pupil diameter and distance,small distortion for virtual image,and see-through light paths are pivotal factors to achieve a better,wearable experience of optical see-through headmounted displays(OST-HMDs).In addition,light efficiency of the virtual image light path is an important factor for heat dissipation in HMD devices.This paper presents a new type of OST-HMD optical system that includes three wedge-shaped freeform prisms and two symmetric lenses.Based on a 0.71 in.microdisplay,an OST-HMD prototype with a diagonal field of view(FOV)of 45.3°,an F-number(F/#)of 1.8,an exit pupil size of 12 mm×8 mm,and an eye relief of 18 mm is demonstrated.The maximum value of distortion of the final system is 0.6%and 0.4%for virtual image and see-through light path,respectively.The overall dimension of the optical system per eye is no larger than 30 mm(width)×40 mm(height)×14 mm(thickness),and the weight of the optical module including lenses,holder,and microdisplay is 12.8 g.The light efficiency of the virtual image light path is up to 50%higher than those of other OST-HMD optical solutions.展开更多
It is still very challenging to determine a freeform lens for converting a given input beam into a prescribed output beam where not only the irradiance distribution but also the phase distribution hardly can be expres...It is still very challenging to determine a freeform lens for converting a given input beam into a prescribed output beam where not only the irradiance distribution but also the phase distribution hardly can be expressed analytically.Difficulties arise because the ray mapping from the input beam to the output beam is not only intertwined with the required double freeform surfaces but also intertwined with the output phase distribution,whose gradient represents the directions of the output rays.Direct determination of such a problem is very difficult.Here,we develop a special iterative wavefront tailoring(IWT)method to tackle this problem.In a certain iteration,the current calculation data of the double freeform surfaces and the output phase gradient are used to update the coefficients of a Monge–Ampère equation describing an intermediate wavefront next to the entrance freeform surface.The solution to the wavefront equation could lead to an improved ray mapping to be used to update the corresponding phase gradient data and reconstruct the double freeform surfaces.In a demonstrative example that deviates much from the paraxial or small-angle approximation,the new IWT method can generate a freeform lens that performs much better than that designed by a conventional ray mapping method for producing two irradiance distributions in the forms of numerals"1"and"2"on two successive targets,respectively.展开更多
Using compressive sensing for imaging has many applications, and it is an important branch of computational imaging.In this Letter, freeform surfaces are introduced in the hardware optical system design of a compressi...Using compressive sensing for imaging has many applications, and it is an important branch of computational imaging.In this Letter, freeform surfaces are introduced in the hardware optical system design of a compressive sensing imager. The system works under the medium wave infrared band and realizes a 16× compression with a field-of-view of 7.5°× 6°. Good imaging performance is achieved in both the entire system and the freeform objective optics. Compared with the system using all spherical lenses, the volume of the freeform system is about 1/3 smaller, and the total transmittance is about 56%higher, which shows the benefits of using freeform surfaces for compressive sensing and computational imaging.展开更多
Retinal projection displays （RPDs） are an important development direction for head-mounted dis- plays （HMDs）. This paper reviews the literature on optical engineering aspects based on the data on advanced technolo...Retinal projection displays （RPDs） are an important development direction for head-mounted dis- plays （HMDs）. This paper reviews the literature on optical engineering aspects based on the data on advanced technology in RPD design and development. The review includes the principles and applications of four theories, e. g., the Maxwellian view and its modified modality and the monocular and binocular depth cues of stereoscopic objects in the physiology of the human visual system. To support the Maxwellian view and achieve retinal projec- tion systems with depth cues, results of previous design works were summarized using different methods and their advantages and disadvantages are analyzed. With an extremely long focal depth, a prototype of a full-color stereoscopic see-through RPD system was discussed. Finally, a brief outlook of the future development trends and applications of the RPDs was presented展开更多
Augmented reality head-mounted displays(AR-HMDs)enable users to see real images of the outside world and visualize virtual information generated by a computer at any time and from any location,making them useful for v...Augmented reality head-mounted displays(AR-HMDs)enable users to see real images of the outside world and visualize virtual information generated by a computer at any time and from any location,making them useful for various applications.The manufacture of AR-HMDs combines the fields of optical engineering,optical materials,optical coating,precision manufacturing,electronic science,computer science,physiology,ergonomics,etc.This paper primarily focuses on the optical engineering of AR-HMDs.Optical combiners and display devices are used to combine real-world and virtual-world objects that are visible to the human eye.In this review,existing AR-HMD optical solutions employed for optical combiners are divided into three categories:optical solutions based on macro-,micro-,and nanooptics.The physical principles,optical structure,performance parameters,and manufacturing process of different types of AR-HMD optical solutions are subsequently analyzed.Moreover,their advantages and disadvantages are investigated and evaluated.In addition,the bottlenecks and future development trends in the case of AR-HMD optical solutions are discussed.展开更多
Since the invention of holography by Dennis Gabor,the fabrication of holograms has mainly relied on direct recording of wavefront by engraving the intensity fringes of interfering electric fields into the holographic ...Since the invention of holography by Dennis Gabor,the fabrication of holograms has mainly relied on direct recording of wavefront by engraving the intensity fringes of interfering electric fields into the holographic material.The degree-of-freedom(DoF)is often limited,especially for its usage as a holographic optical element in imaging or display systems,as what is recorded is what to use.In this work,based on the emerging self-assembled photo-aligned liquid crystal,a polarization hologram with full DoF for local manipulation of optical structure is demonstrated.The ability to record an arbitrary wavefront(in-plane DoF)is achieved by freeform surface exposure,while the local adjustment of deposited liquid crystal(out-of-plane DoF)is realized by inkjet printing.The methodology for designing and fabricating such a hologram is exemplified by building a full-color retinal scanning display without color crosstalk.Here,the arbitrary wavefront modulation capability helps to eliminate the aberrations caused by mismatched exposure and display wavelengths.The local liquid crystal adjustment ability enables the suppression of crosstalk by variation of chiral pitch and film thickness to tune the peak and valley of Bragg diffraction band.The demonstrated method is expected to greatly impact the fields of advanced imaging and display,such as augmented reality and virtual reality,that require optics with an ultrathin form factor and high degrees of design freedom simultaneously.展开更多
We implement Monte Carlo-based parallel ray tracing to achieve quick irradiance evaluation for freeform lenses with nonuniform rational B-splines(NURBS)surfaces.We employ the inverse transform sampling method to sampl...We implement Monte Carlo-based parallel ray tracing to achieve quick irradiance evaluation for freeform lenses with nonuniform rational B-splines(NURBS)surfaces.We employ the inverse transform sampling method to sample rays uniformly from the Lambertian light source and adopt the analytical form of the B-spline basis function to achieve fast surface interpolation.When performing parallel calculations for the intersections between the rays and the NURBS surfaces,we propose a parameter transformation method to avoid the parameters escaping from the defined range in the iteration process.Simulation results of two complex picture-generating freeform lenses show that our method is fast and effective.展开更多
Using freeform optical surfaces in lens design can lead to much higher system specifications and performance while significantly reducing volume and weight.However,because of the complexity of freeform surfaces,freefo...Using freeform optical surfaces in lens design can lead to much higher system specifications and performance while significantly reducing volume and weight.However,because of the complexity of freeform surfaces,freeform optical design using traditional methods requires extensive human effort and sufficient design experience,while other design methods have limitations in design efficiency,simplicity,and versatility.Deep learning can solve these issues by summarizing design knowledge and applying it to design tasks with different system and structure parameters.We propose a deep-learning framework for designing freeform imaging systems.We generate the data set automatically using a combined sequential and random system evolution method.We combine supervised learning and unsupervised learning to train the network so that it has good generalization ability for a wide range of system and structure parameter values.The generated network FreeformNet enables fast generation(less than 0.003 s per system)of multiple-solution systems after we input the design requirements,including the system and structure parameters.We can filter and sort solutions based on a given criterion and use them as good starting points for quick final optimization(several seconds for systems with small or moderate field-of-view in general).The proposed framework presents a revolutionary approach to the lens design of freeform or generalized imaging systems,thus significantly reducing the time and effort expended on optical design.展开更多
基金We are grateful for financial supports from National Key Research and Development Program(Grant No.2017YFA0701200)National Science Foundation of China(No.11704030).The author Z X Feng thanks the valuable discussions with Xu-Jia Wang and Rengmao Wu.
文摘Current freeform illumination optical designs are mostly focused on producing prescribed irradiance distributions on planar targets.Here,we aim to design freeform optics that could generate a desired illumination on a curved target from a point source,which is still a challenge.We reduce the difficulties that arise from the curved target by involving its varying z-coordinates in the iterative wavefront tailoring(IWT)procedure.The new IWT-based method is developed under the stereographic coordinate system with a special mesh transformation of the source domain,which is suitable for light sources with light emissions in semi space such as LED sources.The first example demonstrates that a rectangular flat-top illumination can be generated on an undulating surface by a spherical-freeform lens for a Lambertian source.The second example shows that our method is also applicable for producing a non-uniform irradiance distribution in a circular region of the undulating surface.
基金supported by the National Science Foundation of China(grant nos.62475015,62305024,12027807,62225501)National Key Research and Development Program of China(grant nos.2021YFB2802100,2020YFA0211300)+1 种基金Young Elite Scientist Sponsorship Program by CAST(grant no.YESS20220080)Beijing Institute of Technology Research Fund Program for Young Scholars(grant no.XSQD-202204007).
文摘The development of color routers(CRs)realizes the splitting of dichromatic components,contributing to the modulation of photon momentum that acts as the information carrier for optical information technology on the frequency and spatial domains.However,CRs with optical stimulation lack active control of photon momentum at deep subwavelength scale because of the optical diffraction limit.Here,we experimentally demonstrate an active manipulation of dichromatic photon momentum at a deep subwavelength scale via electron-induced CRs,where the CRs radiation patterns are manipulated by steering the electron impact position within 60 nm in a single nanoantenna unit.Moreover,an encrypted display device based on programmable modulation of the CR array is designed and implemented.This approach with enhanced security,large information capacity,and high-level integration at a deep subwavelength scale may find applications in photonic devices and emerging areas in quantum information technologies.
基金National Key Research and Development Program of China(2017YFA0701200)National Natural Science Foundation of China(61822502)Beijing Municipal Science Technology Commission(Z201100004020011)。
文摘Compactness and light weight,large exit pupil diameter and distance,small distortion for virtual image,and see-through light paths are pivotal factors to achieve a better,wearable experience of optical see-through headmounted displays(OST-HMDs).In addition,light efficiency of the virtual image light path is an important factor for heat dissipation in HMD devices.This paper presents a new type of OST-HMD optical system that includes three wedge-shaped freeform prisms and two symmetric lenses.Based on a 0.71 in.microdisplay,an OST-HMD prototype with a diagonal field of view(FOV)of 45.3°,an F-number(F/#)of 1.8,an exit pupil size of 12 mm×8 mm,and an eye relief of 18 mm is demonstrated.The maximum value of distortion of the final system is 0.6%and 0.4%for virtual image and see-through light path,respectively.The overall dimension of the optical system per eye is no larger than 30 mm(width)×40 mm(height)×14 mm(thickness),and the weight of the optical module including lenses,holder,and microdisplay is 12.8 g.The light efficiency of the virtual image light path is up to 50%higher than those of other OST-HMD optical solutions.
基金National Key Research and Development Program of China(2018YFB0406800)National Natural Science Foundation of China(11704030)。
文摘It is still very challenging to determine a freeform lens for converting a given input beam into a prescribed output beam where not only the irradiance distribution but also the phase distribution hardly can be expressed analytically.Difficulties arise because the ray mapping from the input beam to the output beam is not only intertwined with the required double freeform surfaces but also intertwined with the output phase distribution,whose gradient represents the directions of the output rays.Direct determination of such a problem is very difficult.Here,we develop a special iterative wavefront tailoring(IWT)method to tackle this problem.In a certain iteration,the current calculation data of the double freeform surfaces and the output phase gradient are used to update the coefficients of a Monge–Ampère equation describing an intermediate wavefront next to the entrance freeform surface.The solution to the wavefront equation could lead to an improved ray mapping to be used to update the corresponding phase gradient data and reconstruct the double freeform surfaces.In a demonstrative example that deviates much from the paraxial or small-angle approximation,the new IWT method can generate a freeform lens that performs much better than that designed by a conventional ray mapping method for producing two irradiance distributions in the forms of numerals"1"and"2"on two successive targets,respectively.
基金This work was supported by the National Key Research and Development Program of China(No.2017YFA0701200)National Natural Science Foundation of China(No.61805012)Young Elite Scientist Sponsorship Program by CAST(No.2019QNRC001)。
文摘Using compressive sensing for imaging has many applications, and it is an important branch of computational imaging.In this Letter, freeform surfaces are introduced in the hardware optical system design of a compressive sensing imager. The system works under the medium wave infrared band and realizes a 16× compression with a field-of-view of 7.5°× 6°. Good imaging performance is achieved in both the entire system and the freeform objective optics. Compared with the system using all spherical lenses, the volume of the freeform system is about 1/3 smaller, and the total transmittance is about 56%higher, which shows the benefits of using freeform surfaces for compressive sensing and computational imaging.
文摘Retinal projection displays （RPDs） are an important development direction for head-mounted dis- plays （HMDs）. This paper reviews the literature on optical engineering aspects based on the data on advanced technology in RPD design and development. The review includes the principles and applications of four theories, e. g., the Maxwellian view and its modified modality and the monocular and binocular depth cues of stereoscopic objects in the physiology of the human visual system. To support the Maxwellian view and achieve retinal projec- tion systems with depth cues, results of previous design works were summarized using different methods and their advantages and disadvantages are analyzed. With an extremely long focal depth, a prototype of a full-color stereoscopic see-through RPD system was discussed. Finally, a brief outlook of the future development trends and applications of the RPDs was presented
文摘Augmented reality head-mounted displays(AR-HMDs)enable users to see real images of the outside world and visualize virtual information generated by a computer at any time and from any location,making them useful for various applications.The manufacture of AR-HMDs combines the fields of optical engineering,optical materials,optical coating,precision manufacturing,electronic science,computer science,physiology,ergonomics,etc.This paper primarily focuses on the optical engineering of AR-HMDs.Optical combiners and display devices are used to combine real-world and virtual-world objects that are visible to the human eye.In this review,existing AR-HMD optical solutions employed for optical combiners are divided into three categories:optical solutions based on macro-,micro-,and nanooptics.The physical principles,optical structure,performance parameters,and manufacturing process of different types of AR-HMD optical solutions are subsequently analyzed.Moreover,their advantages and disadvantages are investigated and evaluated.In addition,the bottlenecks and future development trends in the case of AR-HMD optical solutions are discussed.
基金National Key Research and Development Program of China(2021YFB2802100).
文摘Since the invention of holography by Dennis Gabor,the fabrication of holograms has mainly relied on direct recording of wavefront by engraving the intensity fringes of interfering electric fields into the holographic material.The degree-of-freedom(DoF)is often limited,especially for its usage as a holographic optical element in imaging or display systems,as what is recorded is what to use.In this work,based on the emerging self-assembled photo-aligned liquid crystal,a polarization hologram with full DoF for local manipulation of optical structure is demonstrated.The ability to record an arbitrary wavefront(in-plane DoF)is achieved by freeform surface exposure,while the local adjustment of deposited liquid crystal(out-of-plane DoF)is realized by inkjet printing.The methodology for designing and fabricating such a hologram is exemplified by building a full-color retinal scanning display without color crosstalk.Here,the arbitrary wavefront modulation capability helps to eliminate the aberrations caused by mismatched exposure and display wavelengths.The local liquid crystal adjustment ability enables the suppression of crosstalk by variation of chiral pitch and film thickness to tune the peak and valley of Bragg diffraction band.The demonstrated method is expected to greatly impact the fields of advanced imaging and display,such as augmented reality and virtual reality,that require optics with an ultrathin form factor and high degrees of design freedom simultaneously.
基金supported by the National Key Research and Development Program of China(No.2017YFA0701200)the National Natural Science Foundation of China(No.11704030)the CAAI-Huawei MindSpore Open Fund(No.CAAIXSJLJJ-2021-014A)。
文摘We implement Monte Carlo-based parallel ray tracing to achieve quick irradiance evaluation for freeform lenses with nonuniform rational B-splines(NURBS)surfaces.We employ the inverse transform sampling method to sample rays uniformly from the Lambertian light source and adopt the analytical form of the B-spline basis function to achieve fast surface interpolation.When performing parallel calculations for the intersections between the rays and the NURBS surfaces,we propose a parameter transformation method to avoid the parameters escaping from the defined range in the iteration process.Simulation results of two complex picture-generating freeform lenses show that our method is fast and effective.
基金National Key Research and Development Program of China(2022YFB3603400)National Natural Science Foundation of China(62275019,U21A20140)Young Elite Scientist Sponsorship Program by CAST(2019QNRC001)。
文摘Using freeform optical surfaces in lens design can lead to much higher system specifications and performance while significantly reducing volume and weight.However,because of the complexity of freeform surfaces,freeform optical design using traditional methods requires extensive human effort and sufficient design experience,while other design methods have limitations in design efficiency,simplicity,and versatility.Deep learning can solve these issues by summarizing design knowledge and applying it to design tasks with different system and structure parameters.We propose a deep-learning framework for designing freeform imaging systems.We generate the data set automatically using a combined sequential and random system evolution method.We combine supervised learning and unsupervised learning to train the network so that it has good generalization ability for a wide range of system and structure parameter values.The generated network FreeformNet enables fast generation(less than 0.003 s per system)of multiple-solution systems after we input the design requirements,including the system and structure parameters.We can filter and sort solutions based on a given criterion and use them as good starting points for quick final optimization(several seconds for systems with small or moderate field-of-view in general).The proposed framework presents a revolutionary approach to the lens design of freeform or generalized imaging systems,thus significantly reducing the time and effort expended on optical design.
