Author Affiliations
1School of Optics and Photonics, Beijing Institute of Technology, Beijing 100081, China2Beijing Engineering Research Center for Mixed Reality and Advanced Display Technology, Beijing 100081, China3Key Laboratory of Photoelectronic Imaging Technology and System, Ministry of Education, Beijing 100081, Chinashow less
Fig. 1. Schematic diagram of diffraction problem model
Fig. 2. Schematic diagram of diffraction design method
Fig. 3. Schematic diagram of design method based on interference principle
[11] Fig. 4. Design examples of Diffraction Tools @ BIT
[21-22]. (a) Intensity distribution of original image; (b) intensity distribution of reconstructed image; (c) reconstruction error varying with number of iterations; (d) optical setup of image decryption system with polarization DOE; (e) designed surface relief pattern of polarized DOE; (f) decryption image
Fig. 5. Schematic diagram of two DOEs and two output layers
[67] Fig. 6. Diffraction deep neural network based on DOE
[69]. (a) DOEs manufactured by 3D printing; (b) schematic diagram of cascaded DOEs for handwritten digit classification
Fig. 7. Algorithm flow chart for designing DOE that can generate beam with ultrahigh aspect ratio
[89] Fig. 8. DOE that can realize controllable spin beam
[101]. (a) DOE phase distribution;(b) spin light field distribution at different exit distances
Fig. 9. DOE for spectral separation
[103] Fig. 10. Polarization filter array and focal plane array sensor
[124] Fig. 11. Reasons for astigmatism in HOE
[141] Fig. 12. Two methods for processing and optimizing DOE
[142]. (a) Using refractive freeform surface element; (b) using holographic printing system
Algorithm | Type | Characteristic of solution | Advantage | Limitation |
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GS algorithm | Iteration | Local optimum | High calculation speed,simple structure | Sensitive to initial conditions,only applicable to unitary optical transformation system | YG algorithm | Iteration | Local optimum | High calculation speed,suitable for any optical transformation system | Sensitive to initial conditions | Hill-Climbing algorithm | Search | Local optimum | Simple structure | Sensitive to initial conditions,low calculation speed | SA algorithm | Search | Global optimum | Simple structure,strong robustness | Slow convergence,sensitive to parameter | Genetic algorithm | Search | Global optimum | Parallel operation | Slow evolution,premature convergence | Deep learning | Learning | Global optimum | Accurate results,high calculation speed | Long training time,sensitive to training data |
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Table 1. Comparison of common design algorithms
Software | Developer | Principle | Major function | Characteristic |
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Virtuallab Fusion | Jena University,Germany | Diffraction and interference of light | Component and system design for imaging,detection and shaping | Solver integrating geometry and wave optics | DOE Master | Light Soft,America | Diffraction and interference of light | Design of DOE | Multiple optimization algorithms,design cascade DOE | Diffraction Tools @ BIT | Beijing Institute of Technology,China | Diffraction,interference and polarization of light | Design of micro-optics and DOE | Multiple design modules, joint optimization of complex optical systems |
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Table 2. Common auxiliary tools for designing DOE
Fabrication method | Mask | Projection system | Point-by-point method | Source of error |
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Binary mask lithography[26] | √ | × | × | Mask alignment,line width,depth | Grayscale mask lithography[27-28] | √ | × | × | Nonlinear error | Thin film deposition technology[29] | √ | × | × | Mask alignment,coating thickness | Particle beam projection lithography[30] | √ | √ | × | Mask displacement,mask deformation,particle scattering | Sub-wavelength holographic lithography[31-35] | √ | × | × | Holographic mask calculation,mask alignment | Diamond turning[36] | × | × | √ | Residual knife mark,surface profile | Particle beam direct writing lithography[37-38] | × | × | √ | Proximity effect,substrate location,processing environment | Imprint[39-40] | × | × | × | Mold,viscous deformation,elastic deformation | Injection molding[41] | × | × | × | Mold,viscous deformation,elastic deformation | Digital lithography[42-46] | × | × | × | Discrete of DMD pixel elements,illumination uniformity | Femtosecond laser direct writing[47-49] | × | × | √ | Mechanical displacement,proximity effect | Laser interference lithography[50-53] | × | × | × | Material nonlinearity,loss of high frequency |
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Table 3. Comparison of DOE processing methods
Material | Function | Tuning mode | Mask | Response time | Driving voltage |
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Liquid crystal[159] | Switchable | Electrical | × | 15 ms/50 ms | 20 V | Azo-benzene functionalized polymer film[161] | Rewritable | Electrical/optical/thermal | × | Dozens of minutes | 8 kV@130 ℃ | Liquid crystal[162] | Switchable | Electrical | × | | 6 V | Hybrid nematic liquid crystal[164] | Switchable/ rewritable | Electrical/optical | √ | 1 ms | | Blue phase liquid crystal[163] | Switchable | Electrical | × | 545 μs/673 μs | 180 V | Chiral liquid crystals[166] | Rewritable | Electrical/optical | × | 100 μs | ~175 V | Blue phase liquid crystal[165] | Rewritable | Electrical/optical | √ | 16 min | 10 V | Liquid crystal[167] | Tunable | Optical | √ | 24 min | | Holographic polymer-dispersed Liquid crystals[169] | Rewritable | Optical | × | 40 s | | Cholesteric liquid crystal[168] | Rewritable | Optical | √ | 17 min/90 s | 10 V(erase) |
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Table 4. Parameters of typical dynamic DOE