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Geometric Optics|35 Article(s)
Design of Off-Axis All-Reflective Three-Gear Zoom Optical System with Long Focal Length
Yiqing Cao
The zoom principle and primary aberration theory are used to study the design method of a mechanically compensated all-off-axis reflective three-gear zoom optical system with long focal length. The initial structure solving model for coaxial four-reflective mirrors zoom optical system is developed and based on the model, the adaptive variant probability genetic algorithm developed is used to address it and the partial initial structure parameters of the coaxial system is obtained; further, it is properly made off-center and tilt to remove the central obscuration issue of the coaxial optical system, and the aberration of the off-axial system is corrected using optical design software Zemax. Using the design method discussed above, an aspheric surface design is adopt in the optical surfaces of the system’s all-reflective mirrors, yielding a high imaging quality off-axis four-reflective mirrors zoom optical system with three-gear zoom focal lengths of 300 mm, 600 mm, and 900 mm. The results show that the method provides an effective measure for an off-axis all-reflective three-gear zoom optical system and that the system can be designed to meet practical needs. The zoom principle and primary aberration theory are used to study the design method of a mechanically compensated all-off-axis reflective three-gear zoom optical system with long focal length. The initial structure solving model for coaxial four-reflective mirrors zoom optical system is developed and based on the model, the adaptive variant probability genetic algorithm developed is used to address it and the partial initial structure parameters of the coaxial system is obtained; further, it is properly made off-center and tilt to remove the central obscuration issue of the coaxial optical system, and the aberration of the off-axial system is corrected using optical design software Zemax. Using the design method discussed above, an aspheric surface design is adopt in the optical surfaces of the system’s all-reflective mirrors, yielding a high imaging quality off-axis four-reflective mirrors zoom optical system with three-gear zoom focal lengths of 300 mm, 600 mm, and 900 mm. The results show that the method provides an effective measure for an off-axis all-reflective three-gear zoom optical system and that the system can be designed to meet practical needs.
Laser & Optoelectronics Progress
- Publication Date: Oct. 10, 2023
- Vol. 60, Issue 19, 1908001 (2023)
Simulation and Design of Wireless Energy Transmission System Based on Visible Light
Xuegui Zhu, Yang Zhou, Huaiqing Zhang, and Wenchao Yu
Aiming at the power supply problem in medium-distance and strong electromagnetic interference environments such as rocket ignition and wireless sensing, a visible light wireless energy transmission system is designed, which uses visible light to achieve wireless energy supply at a distance of several meters. The optical model of the visible light wireless energy transmission system was established by the optical simulation software, the influence of the axial defocus of the light source and the displacement of the plano-convex lens on the light energy utilization rate, the uniformity of the spot, and the photoelectric conversion efficiency were analyzed, and the experimental parameters of the system were determined, which provides a basis for the realization of higher-power, longer-distance, and higher-efficiency visible light wireless energy transmission and variable-distance transmission automatic devices. Experimental results show that the use of a combination of reflective and condensing lenses greatly reduces beam scattering and effectively improves the energy transmission efficiency of the visible light wireless energy transmission system. The system helps to cover the the meter-level blind area, and provide the power supply at a low cost for the low power devices in some extreme environments where battery replacement is inconvenient and electromagnetic interference is serious. Aiming at the power supply problem in medium-distance and strong electromagnetic interference environments such as rocket ignition and wireless sensing, a visible light wireless energy transmission system is designed, which uses visible light to achieve wireless energy supply at a distance of several meters. The optical model of the visible light wireless energy transmission system was established by the optical simulation software, the influence of the axial defocus of the light source and the displacement of the plano-convex lens on the light energy utilization rate, the uniformity of the spot, and the photoelectric conversion efficiency were analyzed, and the experimental parameters of the system were determined, which provides a basis for the realization of higher-power, longer-distance, and higher-efficiency visible light wireless energy transmission and variable-distance transmission automatic devices. Experimental results show that the use of a combination of reflective and condensing lenses greatly reduces beam scattering and effectively improves the energy transmission efficiency of the visible light wireless energy transmission system. The system helps to cover the the meter-level blind area, and provide the power supply at a low cost for the low power devices in some extreme environments where battery replacement is inconvenient and electromagnetic interference is serious.
Laser & Optoelectronics Progress
- Publication Date: Aug. 10, 2023
- Vol. 60, Issue 15, 1508001 (2023)
Distortion Correction of Visual Measurement in Inhomogeneous Temperature Field Based on Ray Tracing Method
Jun Wu, Yuheng Zhu, Shaobo Yuan, Shaoyu Liu, and Meimiao Zhang
In this study, to address the issue of imaging distortion that occurs when visual measurements are applied in inhomogeneous refractive index environments, an inhomogeneous refractive index field produced in the inhomogeneous temperature field is developed, and the trajectory of light in the refractive index field is investigated, and the image distortion is corrected according to the trajectory's deviation. The spatial refractive index field produced using the nonuniform temperature field is reconstructed using the background schlieren method. The light emitted by the spatial point is abstracted as light rays and reproduces the light in the inhomogeneous temperature gradient environment according to the Runge-Kutta method. The world coordinates of the point are computed based on the PnP (perspective-n-point) algorithm and the pixel coordinates of the same point in the image before and after correction. Experimental findings demonstrate that the method can efficiently decrease the measurement error and correct the measured image's distortion. In this study, to address the issue of imaging distortion that occurs when visual measurements are applied in inhomogeneous refractive index environments, an inhomogeneous refractive index field produced in the inhomogeneous temperature field is developed, and the trajectory of light in the refractive index field is investigated, and the image distortion is corrected according to the trajectory's deviation. The spatial refractive index field produced using the nonuniform temperature field is reconstructed using the background schlieren method. The light emitted by the spatial point is abstracted as light rays and reproduces the light in the inhomogeneous temperature gradient environment according to the Runge-Kutta method. The world coordinates of the point are computed based on the PnP (perspective-n-point) algorithm and the pixel coordinates of the same point in the image before and after correction. Experimental findings demonstrate that the method can efficiently decrease the measurement error and correct the measured image's distortion.
Laser & Optoelectronics Progress
- Publication Date: Jan. 10, 2023
- Vol. 60, Issue 1, 0108001 (2023)
Analysis of Light Concentration Error and Compensation Algorithm of Linear Fresnel Collector
Zhiyong Zhang, Linggang Kong, Duojin Fan, and Xiaoming Yao
The focusing precision of the linear Fresnel collector has an important effect on the photothermal efficiency. Moreover, the partial hot spot caused by the partial focus of the concentrator causes an unbalanced expansion of the absorber, which causes severe damage to the collector's structure. Therefore, it is crucial to analyze the concentrating error of the collector. According to the characteristics of the linear Fresnel heat collecting system, the main factors affecting the light-gathering precision of the Fresnel collector are discussed through mechanism analysis. All the factors are analyzed and simulated by MATLAB software, and it is concluded that the main factors that cause the concentration deviation of the collector are the north-south arrangement deviation of the linear Fresnel mirror field, dynamic displacement deviation of the reflection center of the primary mirror, and dynamic variation of the light path of the reflected light. The concentrated light deviation caused by the north-south deviation of the mirror field layout is normally distributed at noon and varies with the latitude. Meanwhile, the effect of the dynamic displacement deviation of the reflection center of the primary mirror on the focusing precision is greater in the morning and evening, and it is asymmetric in the morning and afternoon with the maximum error approaching 0.08°. The influence of light path variation of the reflected light on the concentrating error is mainly reflected in the annual time axis. Through simulation analysis and field testing, the linear compensation algorithm was used to compensate the target tracking angle of the collector's primary mirror. After the compensation, the maximum concentration error of the heat collecting system was less than 0.06°. The focusing precision of the linear Fresnel collector has an important effect on the photothermal efficiency. Moreover, the partial hot spot caused by the partial focus of the concentrator causes an unbalanced expansion of the absorber, which causes severe damage to the collector's structure. Therefore, it is crucial to analyze the concentrating error of the collector. According to the characteristics of the linear Fresnel heat collecting system, the main factors affecting the light-gathering precision of the Fresnel collector are discussed through mechanism analysis. All the factors are analyzed and simulated by MATLAB software, and it is concluded that the main factors that cause the concentration deviation of the collector are the north-south arrangement deviation of the linear Fresnel mirror field, dynamic displacement deviation of the reflection center of the primary mirror, and dynamic variation of the light path of the reflected light. The concentrated light deviation caused by the north-south deviation of the mirror field layout is normally distributed at noon and varies with the latitude. Meanwhile, the effect of the dynamic displacement deviation of the reflection center of the primary mirror on the focusing precision is greater in the morning and evening, and it is asymmetric in the morning and afternoon with the maximum error approaching 0.08°. The influence of light path variation of the reflected light on the concentrating error is mainly reflected in the annual time axis. Through simulation analysis and field testing, the linear compensation algorithm was used to compensate the target tracking angle of the collector's primary mirror. After the compensation, the maximum concentration error of the heat collecting system was less than 0.06°.
Laser & Optoelectronics Progress
- Publication Date: Apr. 10, 2022
- Vol. 59, Issue 7, 0708001 (2022)
Dual-Wavelength Fringe Projection Correction Algorithm Based on Color Segmentation
Jiale Long, Jianmin Zhang, Zihao Du, Fujian Chen, and Haoyuan Guan
Aiming at three-dimensional topography measurement based on structured light projection, a dual-wavelength fringe projection correction algorithm based on color segmentation is proposed in this paper. A color fringe image is added on the basis of the wavelength-selective dual-fringe projection phase unwrapping algorithm, and the fringe image is divided into different fringe regions by color. Phase unwrapping is performed on the phase map by means of a look-up table in different fringe regions. The experimental results show that the algorithm has the advantages of wide measurement range, small amount of calculation, high precision and fast speed. The experimental results show that the algorithm has the advantages of wide measurement range, small amount of calculation, high precision and fast speed, and can effectively solve the problem of repeated lookup tables when the selected wavelength is short. Aiming at three-dimensional topography measurement based on structured light projection, a dual-wavelength fringe projection correction algorithm based on color segmentation is proposed in this paper. A color fringe image is added on the basis of the wavelength-selective dual-fringe projection phase unwrapping algorithm, and the fringe image is divided into different fringe regions by color. Phase unwrapping is performed on the phase map by means of a look-up table in different fringe regions. The experimental results show that the algorithm has the advantages of wide measurement range, small amount of calculation, high precision and fast speed. The experimental results show that the algorithm has the advantages of wide measurement range, small amount of calculation, high precision and fast speed, and can effectively solve the problem of repeated lookup tables when the selected wavelength is short.
Laser & Optoelectronics Progress
- Publication Date: Sep. 10, 2022
- Vol. 59, Issue 17, 1708001 (2022)
Influence of Inclination Angle and Splicing Structure of Cube-Corner Reflector Element on Retroreflection Efficiency
Guang Yang, Minghui Duan, Zhenzhen Li, and Jianhua Chen
Microprism reflector films are limited by various factors, such as a narrow range of effective incidence angles (wide angle) and large difference in retroreflection efficiency at different azimuth angles (different directions). These limitations can be resolved by changing the inclination angle of the cube-corner reflector (CCR) element and using the splicing structure. In this study, CCR arrays with different structures are calculated using the ray-tracing software based on the principle of geometrical optics. Herein, the influence of the inclination angle of the CCR element, angle of the incident light, and the splicing structure on the retroreflection efficiency is analyzed using the retroreflection principle of microprism reflective films. The results show that the retroreflective efficiency in the azimuth 0° direction increases by more than 20 percentage points when using a inclination angle CCR array. Furthermore, the maximum deviation of the retroreflective efficiency in different directions reduces by more than 10% after adopting a spliced structure with different inclination angles. The simulation results of the inclination angle of CCR arrays are compared with rightness test results of the reflective film, and the variation trend of the retroreflective efficiency is found to be consistent, confirming the reliability of the simulation model. These research results can be used in the structural design and optimization of microprism reflective films. Microprism reflector films are limited by various factors, such as a narrow range of effective incidence angles (wide angle) and large difference in retroreflection efficiency at different azimuth angles (different directions). These limitations can be resolved by changing the inclination angle of the cube-corner reflector (CCR) element and using the splicing structure. In this study, CCR arrays with different structures are calculated using the ray-tracing software based on the principle of geometrical optics. Herein, the influence of the inclination angle of the CCR element, angle of the incident light, and the splicing structure on the retroreflection efficiency is analyzed using the retroreflection principle of microprism reflective films. The results show that the retroreflective efficiency in the azimuth 0° direction increases by more than 20 percentage points when using a inclination angle CCR array. Furthermore, the maximum deviation of the retroreflective efficiency in different directions reduces by more than 10% after adopting a spliced structure with different inclination angles. The simulation results of the inclination angle of CCR arrays are compared with rightness test results of the reflective film, and the variation trend of the retroreflective efficiency is found to be consistent, confirming the reliability of the simulation model. These research results can be used in the structural design and optimization of microprism reflective films.
Laser & Optoelectronics Progress
- Publication Date: Jul. 10, 2022
- Vol. 59, Issue 13, 1308002 (2022)
Systematic Error Analysis of Paraxial Object Image Formula for Biconvex Symmetric Ideal Thin Lens
Yun Shao
This study demonstrates that the actual thickness of a convex lens is a problem that cannot be ignored, then gradually deduces the object image relationship and focal length of a biconvex symmetric thick lens in the paraxial case in air. The specific differences in focal length and image distance between thick and thin convex lens theories are revealed through examples and drawings, and some of the rules are analyzed. The approximate expression of the focal length of a thin convex lens and the approximate expression of the focal length error of an ideal thin convex lens are derived using approximation, and the latter is almost independent of the focal length. This study also derives that the approximate expressions of image distances of a thin convex lens and ideal thin convex lens on the condition of “the ratio of object distance to focal length” is greater than 2, and the error between them has nothing to do with the focal length, but only with the thickness, refractive index and “the ratio of object distance to focal length” of the lens. At the end of the study, the reason for setting “the ratio of object distance to focal length” greater than 2 is that it is difficult to take approximation when the object distance is within 2 times the focal length, and the reason for dividing the convex lens into the thick convex lens, ideal thin convex lens, and thin convex lens lies in strict distinction. This study demonstrates that the actual thickness of a convex lens is a problem that cannot be ignored, then gradually deduces the object image relationship and focal length of a biconvex symmetric thick lens in the paraxial case in air. The specific differences in focal length and image distance between thick and thin convex lens theories are revealed through examples and drawings, and some of the rules are analyzed. The approximate expression of the focal length of a thin convex lens and the approximate expression of the focal length error of an ideal thin convex lens are derived using approximation, and the latter is almost independent of the focal length. This study also derives that the approximate expressions of image distances of a thin convex lens and ideal thin convex lens on the condition of “the ratio of object distance to focal length” is greater than 2, and the error between them has nothing to do with the focal length, but only with the thickness, refractive index and “the ratio of object distance to focal length” of the lens. At the end of the study, the reason for setting “the ratio of object distance to focal length” greater than 2 is that it is difficult to take approximation when the object distance is within 2 times the focal length, and the reason for dividing the convex lens into the thick convex lens, ideal thin convex lens, and thin convex lens lies in strict distinction.
Laser & Optoelectronics Progress
- Publication Date: Jul. 10, 2022
- Vol. 59, Issue 13, 1308001 (2022)
Design of Variable Coefficient Ellipsoid Condenser
Huanjie Sun, Guoyu Zhang, Gaofei Sun, Jian Zhang, and Shanchi Ming
In order to solve the problem of low radiation uniformity of a solar simulator, a variable coefficient ellipsoid condenser system was established according to the working principle of solar simulators. Firstly, the high-order equation is obtained by Taylor expansion of the traditional ellipsoid equation, and an ellipsoid equation with variable coefficients is obtained by evolution. Then, the optimal variable coefficient ellipsoid equation is obtained by adjusting the coefficients of the variable coefficient ellipsoid equation. Then, MATLAB is used to simulate the energy at the second focal planes of the variable coefficient ellipsoid and the traditional ellipsoid, and the two are compared. The LIGHTTOOLS software is used to simulate the optical systems of the traditional ellipsoid and the variable coefficient ellipsoidal condenser. The simulation results show that the uniformity of the second focal plane of the variable coefficient ellipsoid is higher than that of the traditional ellipsoid. The radiation uniformity of the variable coefficient ellipsoid is 3.91% higher than that of the traditional ellipsoid, which basically meets the requirements of high radiation uniformity of solar simulators. In order to solve the problem of low radiation uniformity of a solar simulator, a variable coefficient ellipsoid condenser system was established according to the working principle of solar simulators. Firstly, the high-order equation is obtained by Taylor expansion of the traditional ellipsoid equation, and an ellipsoid equation with variable coefficients is obtained by evolution. Then, the optimal variable coefficient ellipsoid equation is obtained by adjusting the coefficients of the variable coefficient ellipsoid equation. Then, MATLAB is used to simulate the energy at the second focal planes of the variable coefficient ellipsoid and the traditional ellipsoid, and the two are compared. The LIGHTTOOLS software is used to simulate the optical systems of the traditional ellipsoid and the variable coefficient ellipsoidal condenser. The simulation results show that the uniformity of the second focal plane of the variable coefficient ellipsoid is higher than that of the traditional ellipsoid. The radiation uniformity of the variable coefficient ellipsoid is 3.91% higher than that of the traditional ellipsoid, which basically meets the requirements of high radiation uniformity of solar simulators.
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 2021
- Vol. 58, Issue 9, 0908001 (2021)
Design of Zoom Lens System with Movable Components Including Large Aperture and with Ultra-Wide Field of View
Zhijuan Shen, Haifeng Lin, and Yiqing Cao
A design method is proposed for achieving ultra-wide field of view and high-resolution imaging in an optical system including a zoom lens with a large aperture. By analyzing the principle of the optical system and comparing the mode of zoom compensation, an all-motion mode of compensation is adopted to enable zoom motion in the entire system. The primary aberration theory and the ZEMAX software program are applied to determine the initial structure parameters. The optimized design includes 14 components for the refraction lens aperture and large field of view zoom system. The parameters include a system working band of 400?700 nm, focal length range of 6.54?17.00 mm, changing time ratio of 2.6, full field of view angle ranges of 60°?178°, and F-number of 2.8. The modulation transfer function value in the Nyquist frequency, at 55.6 lp/mm, is greater than 0.40; therefore, the imaging quality of the proposed system very good and meets the design requirements. A design method is proposed for achieving ultra-wide field of view and high-resolution imaging in an optical system including a zoom lens with a large aperture. By analyzing the principle of the optical system and comparing the mode of zoom compensation, an all-motion mode of compensation is adopted to enable zoom motion in the entire system. The primary aberration theory and the ZEMAX software program are applied to determine the initial structure parameters. The optimized design includes 14 components for the refraction lens aperture and large field of view zoom system. The parameters include a system working band of 400?700 nm, focal length range of 6.54?17.00 mm, changing time ratio of 2.6, full field of view angle ranges of 60°?178°, and F-number of 2.8. The modulation transfer function value in the Nyquist frequency, at 55.6 lp/mm, is greater than 0.40; therefore, the imaging quality of the proposed system very good and meets the design requirements.
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 2021
- Vol. 58, Issue 7, 0708001 (2021)
Research on Athermalization Design of Infrared Optical System Based on Wavefront Coding
Faqiang Zhang, Bin Feng, and Hongshun Li
Athermalization is one of the important aspects of infrared optical system design. This article introduces the principle and method of athermalization design of infrared optical system using wavefront coding technology, analyzes the basic principles of wavefront coding, and gives the expression of modulation transfer function (MTF) of wavefront coding optical system. On this basis, the image quality of the three-plate long-wave infrared optical system at room temperature (+20 ℃), -40 ℃ and +60 ℃ is analyzed by using ZEMAX optical design software. The analysis results show that the imaging quality of the system is close to the diffraction limit at room temperature, but when the temperature changes between -40 ℃ and +60 ℃, the MTF value decreases rapidly and appears zero, indicating that the imaging quality of the system deteriorates sharply and no longer meets the requirements of use. The MTF value is no longer sensitive to temperature when the wavefront coding phase plate is added to the design of dethermal error, and a clearer target image can be obtained at different temperatures, indicating that the wavefront coding technology can realize the athermalization design of the infrared optical system. Athermalization is one of the important aspects of infrared optical system design. This article introduces the principle and method of athermalization design of infrared optical system using wavefront coding technology, analyzes the basic principles of wavefront coding, and gives the expression of modulation transfer function (MTF) of wavefront coding optical system. On this basis, the image quality of the three-plate long-wave infrared optical system at room temperature (+20 ℃), -40 ℃ and +60 ℃ is analyzed by using ZEMAX optical design software. The analysis results show that the imaging quality of the system is close to the diffraction limit at room temperature, but when the temperature changes between -40 ℃ and +60 ℃, the MTF value decreases rapidly and appears zero, indicating that the imaging quality of the system deteriorates sharply and no longer meets the requirements of use. The MTF value is no longer sensitive to temperature when the wavefront coding phase plate is added to the design of dethermal error, and a clearer target image can be obtained at different temperatures, indicating that the wavefront coding technology can realize the athermalization design of the infrared optical system.
Laser & Optoelectronics Progress
- Publication Date: Oct. 29, 2021
- Vol. 58, Issue 22, 2208001 (2021)
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