2023

• Record 361 of
  
  Title:Theoretical and experimental study on responsivity of ultra-fast X-ray semiconductor chip based on the rad-optic effect
  
  Author(s):Yan, Xin(1,2); Wang, Tao(2); Wang, Gang(2); Yao, Dong(1,2); Liu, Yiheng(2); Gao, Guilong(2); Xin, Liwei(1,2); Yin, Fei(2); Tian, Jinshou(2); Chang, Xinlong(1); He, Kai(2)
  Source: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment  Volume: 1049  Issue: null  Article Number: 168070  DOI: 10.1016/j.nima.2023.168070  Published: April 2023  
  Abstract:Semiconductor sensors based on the rad-optic effect enable ultra-fast detection of X-rays and play an important role in fusion diagnostics. Obtaining the responsivity of the semiconductor ultrafast response material is an important part of characterization. In this work, the refractive index change mechanism of the semiconductor under X-ray irradiation was analyzed, and the quantitative relationship between the diffraction efficiency and the X-ray photon energy was established through the LT-AlGaAs diffraction imaging experiments. The impulse responses of LT-AlGaAs under 1 keV–10 keV X-ray radiation were calculated, revealing the variation of responsivity with radiated photon energy. Imaging experiments of LT-AlGaAs were performed by bombarding an Al target to generate 1.5 keV X-rays. The diffraction images were obtained in agreement with the simulations. The responsivity of the semiconductor chip increases with the square of the incident X-ray power density. This study provides meaningful analyses for the development of ultra-fast X-ray imaging systems based on the rad-optic effect. © 2023 Elsevier B.V.
  Accession Number: 20230613549807
• Record 362 of
  
  Title:Real-time image processing of space camera based on FPGA
  
  Author(s):Duan, Jia Xin(1,2); Zhang, Hai Feng(2,3); Zhou, Shun(1); Huang, Ji Jiang(2)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12700  Issue: null  Article Number: 1270022  DOI: 10.1117/12.2682281  Published: 2023  
  Abstract:According to the characteristics of space camera subject to working environment and task requirements, the automatic exposure and automatic white balance are analyzed theoretically. Gaussian weight is used to correlate the target position and gray value of image, and the relationship between variable step size adjustment, balance accuracy and speed of automatic exposure is optimized. Automatic white balance performs color temperature estimation in RGB space, enabling accurate image color restoration under different illumination. The optimized design of hardware implementation according to the FPGA characteristics. Through the simulation software analysis and the effect of the hardware system display pictures, it is shown that the FPGA hardware system can run high-definition real-time, fast speed, low power consumption and strong practicability. This hardware system has been used in image processing of space cameras. © 2023 SPIE.
  Accession Number: 20232614326644
• Record 363 of
  
  Title:Research on data association and detection algorithm in point target tracking
  
  Author(s):He, Xiaokun(1,2); Li, Peng(3); Liu, Wen(1,2)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12963  Issue: null  Article Number: 1296314  DOI: 10.1117/12.3007679  Published: 2023  
  Abstract:In the field of computer vision, point target tracking has always been an important topic and research hotspot, and it is widely used in both military and civilian fields. For the tracking of point targets under complex background, the point targets are extremely small, and their morphological characteristics are not obvious, so they are easily disturbed by background and noise. Secondly, the point targets' maneuvering, shaking of detection equipment, etc., will change their morphology, resulting in low detection rate and high false alarm rate, which will further affect the accuracy and robustness of point target tracking. Therefore, how to effectively utilize the spatio-temporal information in sequence images to extract the target accurately is a difficult problem. This paper summarizes the existing detection and data association algorithms in point target tracking, analyzes their performance and shortcomings, and discusses the development direction of point target tracking algorithm, that is, algorithms based on multi-feature fusion with strong robustness, high accuracy and small calculation. © 2023 SPIE. All rights reserved.
  Accession Number: 20240215330248
• Record 364 of
  
  Title:Study on the Grinding and Polishing Application of Abrasive Particle-Reinforced Magnetorheological Elastomer
  
  Author(s):Guo, Lei(1); Ji, Yunxiao(1); Ma, Zhen(2); Guo, Wanjin(1); Lee, Chulhee(3); Zhang, Xinrong(1)
  Source: Hsi-An Chiao Tung Ta Hsueh/Journal of Xi'an Jiaotong University  Volume: 57  Issue: 10  Article Number: null  DOI: 10.7652/xjtuxb202310014  Published: October 2023  
  Abstract:As conventional rigid abrasive tools struggle to balance machining efficiency, surface quality and integrity when used to deal with hard and brittle materials with complex surface features, a novel abrasive machining method, which used abrasive particle-reinforced magnetorheological elastomer(A-MRE), was proposed in this study. Firstly, a preparation process of A-MRE was designed, considering the chain network assembly behavior of magnetic particles and abrasive grains in the silicone rubber matrix. Then, a representative volume element(RVE)model was established through the observation of microscopic structure. The effect of a magnetic field on the holding behavior of softness consolidation abrasive grains was investigated through theoretical analysis and fem simulation. Finally, an experimental SiC material abrasive machining was carried out using A-MRE tools, and the surface quality and material removal rate were analyzed under different magnetic field conditions. The research results show that the maximum abrasive grain holding stress occurs when the magnetic field direction and the chain direction of the magnetic particles form a 0° angle, and the stress increases with higher magnetic field intensities. When applying a compressive strain of 1.5 μm to the A-MRE tool, the maximum holding stress reaches 396.63 kPa. Comparing the A-MRE tool's machining performance to the case without a magnetic field, it is observed that employing a magnetic field intensity of 0.35 T leads to an 80.3% reduction in SiC material's surface roughness, a 28.6% increase in material removal, and a 56.1% reduction in tool wear. These findings confirm the feasibility of A-MRE as the material of elastic abrasive tools. © 2023 Xi'an Jiaotong University. All rights reserved.
  Accession Number: 20234815140113
• Record 365 of
  
  Title:Grinding and Polishing Test of 3D-printed Superalloy Blade Based on Elastic-matrix Abrasive Tool
  
  Author(s):Guo, Lei(1,2); Wang, Jia-Qing(1); Ming, Zi-Hang(1); Guo, Wan-Jin(1); Ma, Zhen(3); Jin, Qi-Chao(1)
  Source: Surface Technology  Volume: 52  Issue: 2  Article Number: null  DOI: 10.16490/j.cnki.issn.1001-3660.2023.02.005  Published: 2023  
  Abstract:Shape-Adaptive Polishing (SAP) is an effective method for the polishing of hard and brittle materials. The work aims to verify the feasibility of the adaptive grinding and polishing of 3D-printed nickel-based superalloy engine blades with elastic matrix abrasive tools. Firstly, a finite element model of the elastic contact between the polishing tool and the blade was established based on the elastic grinding and polishing techniques with silicon rubber-based abrasive tools. In addition, the stress distribution and material removal function within the contact area were analyzed. Furthermore, the effect of contact deformation and material removal of abrasive tools on trajectory planning was studied according to the finite element analysis. Finally, the reasonable trajectory step size and spacing were determined, where the contact state between the grinding tool and the workpiece was kept unchanged during the grinding and polishing process. The experimental tests were carried out on a desktop CNC machining system. EOSM290 3D printer was employed to fabricate the blade, and the GH4169 nickel-based alloy was selected as the source material. The preparation of the abrasive tool was realized by a molding process, where the Smooth-On Ecoflex 0050 silicon rubber and micron-sized diamond grains were selected as the binder matrix material and abrasives. During the experiment, the rotation axis of the silicon rubber-based abrasive tool was consistently vertical to the blade surface by controlling the position and orientation of the blade. The simulation results showed the elliptical contact area between the elastic tool and the curved surface workpiece. Also, the stress distribution and material removal rate decreased gradually from the ellipse's center to the periphery. The optimal track spacing determined was 9 mm when the compression of the elastic abrasive tool was 3 mm. The optimal track spacing increased with the increasing compression of the elastic abrasive tool. The polished blade surface topography was observed through the optical microscope. The experimental results showed that the blade surface had no noticeable scratches and dents after polished with the adaptive polishing tool and planned trajectory. The reason was that the elastic matrix abrasive tool had excellent flexibility in the polishing process and deformed with the blade surface according to the shape, thereby achieving flexible adaptive and uniform polishing under the condition of ensuring the stability of polishing parameters. A group of 10 sample points was taken in the polishing area of the blade surface for measuring the surface roughness by Mitutoyo SURFTEST SJ-310 roughness meter. The surface roughness value was reduced from 1.846 μm to 0.182 μm, and the standard deviation was decreased from 0.108 μm to 0.026 μm. The blade weight loss before and after polishing was measured by an electronic balance, and the material removal rate was calculated as 3.432×109 μm3/min. In summary, the silicon rubber-based abrasive tool can realize the precision polishing of GH4169 nickel-based alloy blades. The adaptive trajectory planning based on the stress distribution in the contact area of the elastic abrasive tool and the transformation of the workpiece position and orientation is promising to improve the consistency of the surface quality in the blade polishing area. © 2023 Chongqing Wujiu Periodicals Press. All rights reserved.
  Accession Number: 20234414982213
• Record 366 of
  
  Title:Measurement method of optical axis parallelism of continuous zoom camera based on skeleton thinning algorithm
  
  Author(s):Kong, Fanzi(1,2,3); Wang, Huawei(1,3); Fang, Yao(1,3); Kang, Chanchan(1,3); Zhou, Feng(1,2,3)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12963  Issue: null  Article Number: 1296304  DOI: 10.1117/12.2692305  Published: 2023  
  Abstract:Optical axis parallelism is critical to high-quality clear imaging and stable field switching during zooming. In this paper, we propose a fast measurement method of optical axis parallelism based on collimator and image processing technology. Our method improves the measurement accuracy by introducing skeleton thinning algorithm. The method realizes the automatic measurement of the optical axis parallelism during zooming and reduces subjective errors. The experimental results show that the measurement efficiency and accuracy have been improved, confirming the practical value of the method. © 2023 SPIE. All rights reserved.
  Accession Number: 20240215330238
• Record 367 of
  
  Title:F/0.78 High Order Aspheric Surface Testing with Null Compensator and Mapping Distortion Correction
  
  Author(s):Hao, Sanfeng(1,2); Zhang, Jian(1,3); Yang, Jianfeng(1)
  Source: Guangzi Xuebao/Acta Photonica Sinica  Volume: 52  Issue: 2  Article Number: 0212004  DOI: 10.3788/gzxb20235202.0212004  Published: February 2023  
  Abstract:Compared with traditional spherical surfaces，aspheric surfaces own more degrees of freedom，which is beneficial to the light weight，integration and aberration correction of an optical system. In recent years，with the development and progress of high-precision optical manufacturing technology，aspheric surfaces have been widely used in the optical systems design in aerospace，space telephoto and other fields. Meanwhile，the testing of aspheric surfaces，especially high-order aspheric surfaces，is more difficult and is a prerequisite for guiding optical deterministic manufacturing. That is to say，it is not only necessary to realize the testing of aspheric surfaces，but also to be able to give correct guidance for manufacturing based on the testing results. At present，aspheric surfaces testing can be achieved with null lens compensator，but for high-order aspheric surfaces with a small F-number，traditional two-piece lens compensator cannot meet the testing accuracy requirements，and the structure of null lens needs to be further optimized. What's more，the shape of interfermetric image obtained with null lens compensator is inconsistent with that of the mirror under test， that is， mapping distortion. It is worth noting that deterministic manufacturing techniques such as Computer-Controlled Optical Surfacing （CCOS）， Magnetorheological Finishing （MRF），and Ion Beam Figuring（IBF） all require accurate guidance and feedback from interfermetric image，position errors caused by mapping distortion will seriously affect manufacturing efficiency，and even lead to a failure. Therefore，the mapping distortion correction is crucial for the interferometric image to correctly guide deterministic manufacturing. In this paper，not only the design method of high-order aspheric null lens compensator is discussed，but also the mapping distortion correction of interferometric image. Firstly，based on third-order aberration theory and PW method，the initial structure calculation formula of the high-order aspheric three-piece lens compensator is deduced，and the above formula is programmed，which facilitates the null lens compensator design. For an 8th-order even-order aspheric surface with an effective diameter of 314 mm and F/0.78，the initial structural parameters of null lens compensator were obtained by using the calculation formula. Then，it is substituted into the optical design software for scaling and optimization，and finally the design result with PV=0.0096λ，RMS=0.0012λ （λ=632.8 nm）can be obtained，which can meet the high-precision testing requirements. Furthermore，a correction method is proposed to solve the problem of mapping distortion in the interferometric image obtained with null lens compensator. This method combines imaging distortion of null lens and an algorithm for solving null distortion point coordinates，which can conveniently realize the rapid mapping distortion correction. On the one hand，null lens imaging system with high-order aspheric surfaces as object can be obtained by reversing the testing light path，and the imaging distortion is consistent with the mapping distortion，which can be used for mapping distortion correction. On the other hand，since the null distortion point is also the geometric center of the interfermetric image，the least squares method is used to fit the circle boundary in combination with the boundary data of interfermetric image，and then the null distortion point can be obtained. Then，The correction method is used to correct the mapping distortion of the interferometeric image obtained by null lens compensator. After 6 times of magnetorheological finishing based correction results，the surface RMS reduced from 0.270λ to 0.019λ，which verifies the validity and efficiency of this correction method. © 2023 Chinese Optical Society. All rights reserved.
  Accession Number: 20231713946002
• Record 368 of
  
  Title:High-Efficient and Accurate Testing of Egg Freshness Based on IPLS-XGBoost Algorithm and VIS-NIR Spectrum
  
  Author(s):Zhang, Mei-Zhi(1); Zhang, Ning(1,2); Qiao, Cong(1); Xu, Huang-Rong(2); Gao, Bo(2); Meng, Qing-Yang(2); Yu, Wei-Xing(2)
  Source: Guang Pu Xue Yu Guang Pu Fen Xi/Spectroscopy and Spectral Analysis  Volume: 43  Issue: 6  Article Number: null  DOI: 10.3964/j.issn.1000-0593(2023)06-1711-08  Published: June 2023  
  Abstract:In view of the low efficiency and accuracy of the traditional spectral method for egg freshness testing, we propose and demonstrate the study of egg freshness by using the VIS-NIR spectroscopy testing method combined with XGBoost and other algorithms. In our experiments, eggs were under different storage conditions as samples were divided into the training set and testing set for model building and evaluation. The harmonic weighted average (F-measure) and Accuracy were used as the performance evaluation indexes of the classification model. A VIS-NIR spectroscopy system collected the reflection spectra of eggs. The obtained spectral data were then preprocessed and used to build different models for egg freshness evaluation. Various classification algorithms, including random forest (RF), least square regression (PLS), support vector machine (SVM), Multi-layer Perceptual Model (MLP) and XGBoost algorithm, were used. The performance of each model was evaluated in detail. The analysis shows that better training results are obtained in the RF, SVM and XGBoost models with data preprocessed by Savitzky Golay first-derivative (SG-1st-Der) and the PLS and MLP models with data preprocessed by standard normal variables (SNV).The interval partial least squares (IPLS) method was used to select a working waveband for data dimension reduction for models with the raw spectral data preprocessed by SG-1st-Der combing with the RF, SVM and XGBoost algorithms and models with the raw spectral data preprocessed by SNV combining with PLS and MLP algorithms, respectively. Based on the verification using the test set, it can be seen that the IPLS-XGBoost classification model after SG-1st-Der pretreatment performs best. For the conditions of room temperature storage and cold storage, the F-measure reached 92.33% and 90% respectively, and the Accuracy reached 94.44% and 91.67% respectively. Moreover, the computing time of the model for the prediction of test set samples takes only 0.6 s. The results show that the visible-near infrared spectroscopy method combined with the IPLS-XGBoost classification algorithm can be applied in egg freshness evaluation. Compared with traditional methods, this method has advantages in model classification performance, evaluation accuracy and running speed. © 2023 Science Press. All rights reserved.
  Accession Number: 20233114482952
• Record 369 of
  
  Title:Theoretical Study of Near Single-cycle Post Compression for Yb Dopped Lasers
  
  Author(s):Cheng, Qi(1,2); Yuan, Hao(1,2); Cao, Huabao(1); Fu, Yuxi(1)
  Source: Guangzi Xuebao/Acta Photonica Sinica  Volume: 52  Issue: 6  Article Number: 0614002  DOI: 10.3788/gzxb20235206.0614002  Published: June 2023  
  Abstract:The attosecond light source can reveal the macroscopic properties of matter from the microscopic field，so it is widely used in the fields of materials，medicine，atomic and molecular physics，and quantum physics. The common laser for generating attosecond light sources is the Ti∶Sapphire laser with a central wavelength of 800 nm. However，the average power is limited due to the thermal effect limitation. With the deepening of the application of attosecond light sources，high power with a high repetition rate driving laser if highly demanded. In order to achieve the driving laser with short pulse duration，high repetition rate and high pulse energy，Yb-doped lasers，such as Yb∶KGW，Yb∶YAG have been developed rapidly in recent years. However，the pulse duration of the Yb-doped laser is much longer，and it needs to be compressed by a post-compression method in order to obtain few-cycle laser pulses. Noble gas filled hollow core fibers are widely employed for pulse compression，but it is difficult to compress the 515 nm pulses obtained by frequency doubling to a nearly single cycle. Therefore， this paper simulates the compression obtaining few cycle pulses based on the time-domain generalized nonlinear Schrödinger equation satisfied when the pulses are transmitted in a hollow core fiber. The light source in the calculation process refers to the PH2-2mJ-SP laser of Light Conversion Company， the center wavelength is 1 030 nm，the repetition rate is 10 kHz，and the pulse energy is 2mJ. In the simulation，the input pulse with a center wavelength of 515 nm，a pulse energy of 1 mJ，and a pulse duration of 250 fs is employed，which peak power is 4×109 W. In order to achieve controlled spectral broadening with minimum loss in the hollow core fiber，the peak power of the pulse should first be less than the photoionization threshold intensity of the noble gas，which limits the minimum core radius to 50 μm. Besides，the peak power should be lower than the self-focusing threshold in order to avoid self-focusing when the pulse is transmitted in a hollow core fiber，which limits the maximum pressure of the noble gas. For the argon and krypton to be investigated，the maximum pressures are 10 bar and 3.5 bar，respectively. Considering the loss coefficient when the pulse is transmitted in the hollow core fiber，and the broadening factor required to broaden the pulse spectrum to an octave，a preliminary length of 2.5 m and a core radius of 125 um can be determined for the hollow core fiber. On this basis，the frequency spectrum and time domain broadening of the pulses under various gas pressure and propagation length are simulated. Finally，the pulse spectrum can be broadened to an octave. Considering the influence of the broadening factor and transmission efficiency，the length of the hollow core fiber is finally selected as 2.5 m when the argon and krypton are filled at their maximum pressures. After compensating the dispersions，the pulses of 2.91 fs and 2.62 fs can be obtained in argon and krypton，respectively，which are less than two optical cycles. But at this time，the compressed pulses still have some high-order dispersion that cannot be compensated. Thus，we employed the multistage compression method，which avoids introducing too much high-order dispersion. The first stage compression is referenced to the work of HARITON V et al.，who successfully compressed a 515 nm，250 fs pulse to 38 fs in their experiments using a multi-pass cavity. The second stage uses a hollow core fiber. Under the appropriate gas pressure，transmission length，and dispersion compensation，the pulse is compressed to ~ 2 fs，which is close to a single cycle，with significantly reduced high-order dispersion than that from single stage compression. © 2023 Chinese Optical Society. All rights reserved.
  Accession Number: 20233014444751
• Record 370 of
  
  Title:Analysis of Key Parameters of Passive Tropospheric Wind Field Detection Based on Oxygen A-band Absorption Line
  
  Author(s):Liu, Huan(1,2); Feng, Yutao(1); Fu, Di(1,2); Zhao, Hengxiang(1); Kong, Liang(1); Hao, Xiongbo(1); Chang, Chenguang(1,2); Han, Bin(1,2); Wang, Sufeng(1,2)
  Source: Guangzi Xuebao/Acta Photonica Sinica  Volume: 52  Issue: 12  Article Number: 1201001  DOI: 10.3788/gzxb20235212.1201001  Published: December 2023  
  Abstract:Real-time and high-precision wind field data play an important role in improving the accuracy of weather forecasts,ensuring the safety of spacecraft take-off and landing,tracking atmospheric pollutants, and radio sound detection. In the visible light and near-infrared bands,there are three absorption bands formed by the absorption of oxygen molecules,namely the oxygen γ band,the oxygen B band and the oxygen A band. The absorption intensity of the A band is greater than that of the γ band and the B band, and without interference from other gases,it is an ideal atmospheric detection source for tropospheric wind speed. The Doppler asymmetric spatial heterodyne wind measurement technology is a technology based on the Fourier transform of the interferogram to realize the Doppler frequency shift detection of the wind,the tropospheric wind velocity can be retrieved by detecting the Doppler shift of the oxygen A-band absorption line. This paper explores the technical feasibility of using Doppler asymmetric spatial heterodyne to detect the tropospheric atmospheric wind field based on the oxygen A-band absorption line. Based on the ideal instrument model and the 1976 American standard profile,the solar zenith angle is taken as 40°,without considering the influence of clouds,rain,aerosol,and surface reflection. Through the analysis of the integral limb radiation characteristics of the absorption spectrum line observed in the single instantaneous field of view at the entrance pupil of the instrument,the paper simulates the forward simulation interference curve of a single space altitude layer,establishes a mathematical model of the instrument response function from the atmospheric absorption spectral line entrance pupil limb radiation to the interference curve,and two harmonics with the same spatial frequency as the interference curve are used for phase demodulation and wind speed inversion of line-of-sight wind. This method does not require Fourier transform,and can directly process the interferogram data to obtain the phase difference of the interferogram before and after the wind speed is applied,so as to solve the wind speed. At the same time,the algorithm only needs to perform a multiplication calculation,and can quickly realize the wind speed inversion. Based on the absorption line wind measurement theory,the measurement accuracy of tropospheric wind field detection using Doppler asymmetric spatial heterodyne is mainly affected by the interferometer optical parameters, filtering parameters,system noise,instrument stability and etalon off-axis effect. Through the simulation analysis of the influence of various instrument parameters on the results of line-of-sight wind speed retrieval,the optimal value range of the optical system parameters is determined. The results show that for the oxygen absorption line with the center wavelength at 769 nm,when the interferometer asymmetry value is 6.5~6.7 mm,the spectral resolution value is 0.49~0.51 cm-1,the value of the etalon spacing is 0.8~1.4 mm,the fineness coefficient is 30~100,the off-axis angle of the etalon is less than 0.2°,and the transmission peak deviation of the etalon is less than 0.018 cm-1,the signal-to-noise ratio of the interferogram is greater than 40 times,the wind speed retrieval accuracy is better than 8 m/s. The research results can provide a theoretical reference for passive tropospheric wind field detection and related instrument design. © 2023 Chinese Optical Society. All rights reserved.
  Accession Number: 20240815570654
• Record 371 of
  
  Title:A Novel Cost-effective Vivo Facial Detection Technique Based on Snapshot Spectral Imaging Sensor
  
  Author(s):Wang, Zhihai(1,2); Wang, Shuai(1,2); Gao, Bo(1,2); Wang, Tianxin(1,2); Zhao, Lvrong(1,2); Yu, Weixing(1,2)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12963  Issue: null  Article Number: 1296315  DOI: 10.1117/12.3007681  Published: 2023  
  Abstract:In the field of face anti-counterfeiting, there are differences between the reflection spectrum of real faces and simulated faces, which can help us overcome the shortcomings of traditional RGB cameras that are difficult to identify the authenticity of faces. In our work, we designed a face anti-spoofing imaging system based on the snapshot spectral imaging chip, which can be used in face anti-spoofing imaging through the analysis of spectral imaging data. Experiments show that our sensor could reconstruct the spectrum of the face region, establish the spectral databases, and achieve face authenticity recognition under active light source based on deep convolutional neural network, with a face recognition accuracy of 95%. © 2023 SPIE. All rights reserved.
  Accession Number: 20240215330249
• Record 372 of
  
  Title:Regulatory method of 3D Multi-focus Controllable Distribution Based on Computer Generated Holography
  
  Author(s):Zhang, Ruidi(1,2); Chen, Xiaoyi(1,3); Duan, Yaxuan(1,3); Wang, Pu(1,3); Da, Zhengshang(1,3)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12595  Issue: null  Article Number: 125951U  DOI: 10.1117/12.2668871  Published: 2023  
  Abstract:Traditional analytical algorithm needs to combine the transmission functions of grating and lens to generate a computer generated hologram (CGH), so as to realize the distribution of three-dimensional (3D) multi-focal points in space, but the grating phase will inevitably produce high-order diffraction focus, resulting in energy loss, and the traditional analytic algorithm is more suitable for generating array multi-focal distribution with equal spacing. To solve this problem, this paper simplifies the traditional analytical algorithm, and proposes a method that only uses multi-lens phase and random phase superposition to generate the CGH required by the target light location, by changing the focal length of the lens phase, the multi-focus distribution along the z-axial direction of multiple independent focal planes is realized. Then the phase of these different focal planes is superimposed, and a 0~2π random phase modulation is added, which can quickly generate 3D multi-focus distribution with controllable number and position. The simulation results show that the energy uniformity of focal spot on each focal plane is between 89.45% and 98.08%. The experimental results show that the energy uniformity of focal spots on each focal plane is between 88.40% and 96.13%, which is consistent with the simulation results. Compared with traditional analytical algorithm, the proposed method is more universal for multi-focus distribution in 3D space without special requirements of array distribution with equal spacing, and has potential application value in laser processing, holographic optical tweezers, optical communication and other fields. © 2023 SPIE.
  Accession Number: 20232114124231