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Optical Design and Fabrication|352 Article(s)
Design of Underwater Spot Target Tracking Software Based on Qt and MATLAB Mixed Programming
Kaiqiang Wang, Zhe Li, Zhenchong Xing, and Xianxian Ma
Underwater laser communication has significant technological advantages over traditional underwater wireless communication methods such as acoustic, long-wave, and very-long-wave communication. However, the underwater environment makes the signal spot vulnerable to deformation and flicker, thus hindering the establishment and maintenance of a reliable optical link. To overcome this problem, we devise an underwater spot tracking software design approach based on Qt and MATLAB mixed programming. The approach adopts the Mean Shift iterative algorithm for underwater spot target recognition and localization. A mixed programming method of MATLAB and Qt is used to create the software interface, build a water tank experimental platform, and import the spot photographs. Spot target recognition and movement trajectory drawing are realized using the software, thus verifying the effectiveness of the algorithm. The final result is essentially consistent with the actual spot trajectory, and the maximum error offset is 7.28 pixel. Underwater laser communication has significant technological advantages over traditional underwater wireless communication methods such as acoustic, long-wave, and very-long-wave communication. However, the underwater environment makes the signal spot vulnerable to deformation and flicker, thus hindering the establishment and maintenance of a reliable optical link. To overcome this problem, we devise an underwater spot tracking software design approach based on Qt and MATLAB mixed programming. The approach adopts the Mean Shift iterative algorithm for underwater spot target recognition and localization. A mixed programming method of MATLAB and Qt is used to create the software interface, build a water tank experimental platform, and import the spot photographs. Spot target recognition and movement trajectory drawing are realized using the software, thus verifying the effectiveness of the algorithm. The final result is essentially consistent with the actual spot trajectory, and the maximum error offset is 7.28 pixel.
Laser & Optoelectronics Progress
- Publication Date: May. 10, 2024
- Vol. 61, Issue 9, 0922003 (2024)
Optimization Design of the Constraint Method to Repress the Thermal Deformation of Reflecting Mirror
Chao Luo, Biyi Wang, Haibo Yang, Lei Yuan, and Jian Liu
In high-power laser applications, it is common to use reflecting mirrors for controlling the beam, such as beam expansion, redirection and wavefront correction. However, various types of reflecting mirrors in the control system will absorb some of the light energy, forming a non-uniform temperature field, which cause deformation of the reflecting mirrors and ultimately affect the quality of the reflected beams. Since the support method and temperature field jointly determine the deformation of the reflecting mirrors, it is necessary to study the optimal support method for reflecting mirrors in the design of beam control systems. Based on thermoelastic mechanics, the methods to reduce the thermal deformation of reflecting mirrors using different mirror support methods are proposed, the temperature field and deformation of the reflecting mirrors under several common support constraints are quantified and simulated. The total deformation of the mirror, the relative deformation of the spot area, and the wavefront aberration introduced by the relative deformation of the spot area are compared. The results show that the support method with a small area constraint on the back of the reflecting mirror has the smallest relative deformation, and the support method with a rigid constraint on the back of the reflecting mirror has the largest relative deformation. The relative deformation of the mirror with a rigid constraint can be effectively reduced by about 98.4%. The experimental and simulation results are very close in terms of the relative deformation of the mirror in the beam spot area, and the wavefront images are essentially identical. These results provide theoretical support for the selection and design of mirror support in beam control systems. In high-power laser applications, it is common to use reflecting mirrors for controlling the beam, such as beam expansion, redirection and wavefront correction. However, various types of reflecting mirrors in the control system will absorb some of the light energy, forming a non-uniform temperature field, which cause deformation of the reflecting mirrors and ultimately affect the quality of the reflected beams. Since the support method and temperature field jointly determine the deformation of the reflecting mirrors, it is necessary to study the optimal support method for reflecting mirrors in the design of beam control systems. Based on thermoelastic mechanics, the methods to reduce the thermal deformation of reflecting mirrors using different mirror support methods are proposed, the temperature field and deformation of the reflecting mirrors under several common support constraints are quantified and simulated. The total deformation of the mirror, the relative deformation of the spot area, and the wavefront aberration introduced by the relative deformation of the spot area are compared. The results show that the support method with a small area constraint on the back of the reflecting mirror has the smallest relative deformation, and the support method with a rigid constraint on the back of the reflecting mirror has the largest relative deformation. The relative deformation of the mirror with a rigid constraint can be effectively reduced by about 98.4%. The experimental and simulation results are very close in terms of the relative deformation of the mirror in the beam spot area, and the wavefront images are essentially identical. These results provide theoretical support for the selection and design of mirror support in beam control systems.
Laser & Optoelectronics Progress
- Publication Date: May. 10, 2024
- Vol. 61, Issue 9, 0922002 (2024)
Three-Wavelength Wide-Range Fast Frequency Shift Based on Optical Phase-Locked Loop
Yanhui Zhao, Min Yang, Guangli Yu, Jianyong Ding, Weibiao Chen, and Fangren Hu
Three-frequency ratio technology is important for sodium Doppler lidar to detect the temperature and wind field in the mesosphere. To realize this technology, three emitted lasers with 589 nm wavelength (f+, f0, f-) should be frequency stable, the frequency switching speed should be fast and the two frequencies (f+, f-) should be frequency locked to 630 MHz relative to the central frequency (f0). In order to meet the above technical requirements, a scheme based on optical phase-locked loop (OPLL) is proposed to realize three-frequency ratio technology. The OPLL is used to realize frequency offset locking. The frequency offset locking range is ± (200~2500) MHz, the minimum step is 200 kHz and the jitter of the beat signal is within ±50 Hz. By setting the frequency shift value and changing the polarity of the error signal, the wavelength of the slave laser is constantly changed, and the three-wavelength output is realized. The PID (proportional, integral, derivative) circuit is optimized to improve the stability of the beat signal, reduce the frequency switching time and the frequency cutting time is less than 10 ms. The experimental results show that the OPLL system can realize fast switching and locking of three frequencies and meet the technical requirements of three-frequency ratio technology. Three-frequency ratio technology is important for sodium Doppler lidar to detect the temperature and wind field in the mesosphere. To realize this technology, three emitted lasers with 589 nm wavelength (f+, f0, f-) should be frequency stable, the frequency switching speed should be fast and the two frequencies (f+, f-) should be frequency locked to 630 MHz relative to the central frequency (f0). In order to meet the above technical requirements, a scheme based on optical phase-locked loop (OPLL) is proposed to realize three-frequency ratio technology. The OPLL is used to realize frequency offset locking. The frequency offset locking range is ± (200~2500) MHz, the minimum step is 200 kHz and the jitter of the beat signal is within ±50 Hz. By setting the frequency shift value and changing the polarity of the error signal, the wavelength of the slave laser is constantly changed, and the three-wavelength output is realized. The PID (proportional, integral, derivative) circuit is optimized to improve the stability of the beat signal, reduce the frequency switching time and the frequency cutting time is less than 10 ms. The experimental results show that the OPLL system can realize fast switching and locking of three frequencies and meet the technical requirements of three-frequency ratio technology.
Laser & Optoelectronics Progress
- Publication Date: May. 10, 2024
- Vol. 61, Issue 9, 0922001 (2024)
Novel Design of Athermal and Rigid Support Structure for Small- and Medium-Aperture Mirrors
Jian Yuan, and Lei Zhang
A novel rigid support structure is proposed in this paper to solve the contradiction between thermal stability and structural stiffness in small- and medium-aperture space mirrors assembled using traditional flexible supports. Additionally, a high-precision secondary mirror assembly with a clear aperture of ?214 mm is developed for a high-resolution space camera. The combination of a mirror body, cone, support cylinder, and rigid base plate is adopted to realize heat dissipation by extending and optimizing the transmission path of the thermal stress within the assembly. The secondary mirror assembly with a rigid support structure weighs 2.6 kg, and the surface accuracy change has a root-mean-square (RMS) value of 2.573 nm in the simulation under the condition of a 4 °C uniform temperature rise. The inclination and displacement of the mirror body subjected to the gravity test are 2.028" and 0.566 μm, respectively, revealing the outstanding advantages of the proposed scheme over traditional flexible support systems. The measured surface accuracy RMS value of the secondary mirror is 0.0181λ (λ=632.8 nm), and the changes in the surface accuracy at 16 and 24 °C do not exceed 0.0025λ. The fundamental frequency of the assembly reaches 502.1 Hz, and the surface accuracy of the secondary mirror remains relatively unchanged after rapid heat cycles and large-scale vibrations. In the assembling tolerance test, the secondary mirror is only slightly deformed under 0.02 mm unevenness. The proposed rigid support structure can significantly improve the working performance of small- and medium-aperture mirrors and has broad application prospects in the optomechanical structural design of remote sensors. A novel rigid support structure is proposed in this paper to solve the contradiction between thermal stability and structural stiffness in small- and medium-aperture space mirrors assembled using traditional flexible supports. Additionally, a high-precision secondary mirror assembly with a clear aperture of ?214 mm is developed for a high-resolution space camera. The combination of a mirror body, cone, support cylinder, and rigid base plate is adopted to realize heat dissipation by extending and optimizing the transmission path of the thermal stress within the assembly. The secondary mirror assembly with a rigid support structure weighs 2.6 kg, and the surface accuracy change has a root-mean-square (RMS) value of 2.573 nm in the simulation under the condition of a 4 °C uniform temperature rise. The inclination and displacement of the mirror body subjected to the gravity test are 2.028" and 0.566 μm, respectively, revealing the outstanding advantages of the proposed scheme over traditional flexible support systems. The measured surface accuracy RMS value of the secondary mirror is 0.0181λ (λ=632.8 nm), and the changes in the surface accuracy at 16 and 24 °C do not exceed 0.0025λ. The fundamental frequency of the assembly reaches 502.1 Hz, and the surface accuracy of the secondary mirror remains relatively unchanged after rapid heat cycles and large-scale vibrations. In the assembling tolerance test, the secondary mirror is only slightly deformed under 0.02 mm unevenness. The proposed rigid support structure can significantly improve the working performance of small- and medium-aperture mirrors and has broad application prospects in the optomechanical structural design of remote sensors.
Laser & Optoelectronics Progress
- Publication Date: Mar. 10, 2024
- Vol. 61, Issue 5, 0522005 (2024)
Focusing Analysis of Linear Zone Plate with Equal-Width Single-Mode Slits Waveguide Working in Extreme Ultraviolet
Wenxuan Chen, Qing Cao, Changjie Cheng, Chaoyue Li, Jirui Zhu, and Yaxing Mao
With the development of processing technology and the increasing requirement of spatial resolution, the slit widths of linear zone plate have become increasingly small. For slits with different widths on the linear zone plate, the incident uniform plane wave can excite one or more waveguide modes, resulting in inter-mode dispersion and phase differences. Even if there is only single-mode transmission in the slits, the effective refractive index of the fundamental mode is related to the width of the slit, which leads to phase difference of slits with different widths at the exit. To eliminate these phase differences, we propose an equal-width single-mode slit waveguide linear zone plate, study its focusing effect in the extreme ultraviolet band, and establish the corresponding Gaussian far-field analytical model. Numerical simulations based on finite element software confirm the distribution of the Gaussian mode field of fundamental mode, and a calculation based on the Fresnel diffraction integral further confirms the validity of the far-field analytical model. As one example, we design an equal-width single-mode slit waveguide linear zone plate and calculate its normalized one-dimensional light field distribution in the focal plane. With the development of processing technology and the increasing requirement of spatial resolution, the slit widths of linear zone plate have become increasingly small. For slits with different widths on the linear zone plate, the incident uniform plane wave can excite one or more waveguide modes, resulting in inter-mode dispersion and phase differences. Even if there is only single-mode transmission in the slits, the effective refractive index of the fundamental mode is related to the width of the slit, which leads to phase difference of slits with different widths at the exit. To eliminate these phase differences, we propose an equal-width single-mode slit waveguide linear zone plate, study its focusing effect in the extreme ultraviolet band, and establish the corresponding Gaussian far-field analytical model. Numerical simulations based on finite element software confirm the distribution of the Gaussian mode field of fundamental mode, and a calculation based on the Fresnel diffraction integral further confirms the validity of the far-field analytical model. As one example, we design an equal-width single-mode slit waveguide linear zone plate and calculate its normalized one-dimensional light field distribution in the focal plane.
Laser & Optoelectronics Progress
- Publication Date: Mar. 10, 2024
- Vol. 61, Issue 5, 0522004 (2024)
Design of a High-Precision Repeatable Secondary Mirror Deployment Mechanism for Space Cameras
Junwei Song, Xiaoping Tao, Minglin Xu, and Xun Wang
High-resolution imaging in space cameras requires a long focal length, leading to increased distance between the primary and secondary mirrors. Consequently, this results in a larger camera volume and inefficient space utilization. To decrease the launch cost and envelope size of the space camera during launch, a high-precision, repeatable secondary mirror deployment mechanism is designed based on the four-link space structure for the coaxial three-mirror optical system. The mechanism's error was analyzed, and finite element analysis was conducted to evaluate its reliability. Additionally, a repeatability test plan was devised to ensure the mechanism's consistency. Following the folding of the secondary mirror deployment mechanism, the optical axis direction length of the space camera is reduced from 875 mm to 324 mm, achieving a 63% compression in volume. In its unfolded state, the mechanism exhibits a fundamental frequency of 96.64 Hz. The maximum deviation in repeated unfolding displacement is measured at 15.61 μm, and the maximum inclination deviation is 16.89″. These results demonstrate the mechanism's effectiveness in minimizing the space camera's volume and meeting the in-orbit requirements, attributable to its locked state fundamental frequency. Furthermore, the mechanism maintains the optical system's repeatability and can accommodate the payload conditions of micro and nano satellites, making it an ideal solution for aerospace applications. High-resolution imaging in space cameras requires a long focal length, leading to increased distance between the primary and secondary mirrors. Consequently, this results in a larger camera volume and inefficient space utilization. To decrease the launch cost and envelope size of the space camera during launch, a high-precision, repeatable secondary mirror deployment mechanism is designed based on the four-link space structure for the coaxial three-mirror optical system. The mechanism's error was analyzed, and finite element analysis was conducted to evaluate its reliability. Additionally, a repeatability test plan was devised to ensure the mechanism's consistency. Following the folding of the secondary mirror deployment mechanism, the optical axis direction length of the space camera is reduced from 875 mm to 324 mm, achieving a 63% compression in volume. In its unfolded state, the mechanism exhibits a fundamental frequency of 96.64 Hz. The maximum deviation in repeated unfolding displacement is measured at 15.61 μm, and the maximum inclination deviation is 16.89″. These results demonstrate the mechanism's effectiveness in minimizing the space camera's volume and meeting the in-orbit requirements, attributable to its locked state fundamental frequency. Furthermore, the mechanism maintains the optical system's repeatability and can accommodate the payload conditions of micro and nano satellites, making it an ideal solution for aerospace applications.
Laser & Optoelectronics Progress
- Publication Date: Mar. 10, 2024
- Vol. 61, Issue 5, 0522003 (2024)
Design and Analysis of a High Flat Tunable Terahertz Electro-Optical Frequency Comb
Wei Zhang, Feng Zhao, Cong Qiao, Andi Liu, Tegang Yan, Yue Cui, and Mingxing Liu
A high-flat broadband optical frequency comb (OFC) signal generation scheme is proposed, and the mechanism and simulation analysis of the signal generation mechanism and method of high-flat and wideband electro-optical comb are carried out. In the simulation analysis, the dual-drive Mach-Zehnder modulator is used to generate the optical frequency comb signal, the phase modulator is used to further increase the number of comb lines, and finally the flatness is improved by jointly optimizing the drive signal power and DC bias voltage of the Mach-Zehnder modulator. The simulation results show that the scheme can generate a broadband comb signal with a bandwidth of 1.08 THz, with a tone-to-noise ratio of 60 dB and a flatness of 0.5 dB. The proposed scheme is applied to the optical carrier terahertz communication system, and the transmission performance of single-channel and multi-channel 16th-order quadrature amplitude modulation (16QAM) terahertz signals in the case of back-to-back (BTB) or 10 km optical fiber transmission is verified by simulation. The results show that the bit error rate in each of the above cases is lower than the threshold of forward error correction code. A high-flat broadband optical frequency comb (OFC) signal generation scheme is proposed, and the mechanism and simulation analysis of the signal generation mechanism and method of high-flat and wideband electro-optical comb are carried out. In the simulation analysis, the dual-drive Mach-Zehnder modulator is used to generate the optical frequency comb signal, the phase modulator is used to further increase the number of comb lines, and finally the flatness is improved by jointly optimizing the drive signal power and DC bias voltage of the Mach-Zehnder modulator. The simulation results show that the scheme can generate a broadband comb signal with a bandwidth of 1.08 THz, with a tone-to-noise ratio of 60 dB and a flatness of 0.5 dB. The proposed scheme is applied to the optical carrier terahertz communication system, and the transmission performance of single-channel and multi-channel 16th-order quadrature amplitude modulation (16QAM) terahertz signals in the case of back-to-back (BTB) or 10 km optical fiber transmission is verified by simulation. The results show that the bit error rate in each of the above cases is lower than the threshold of forward error correction code.
Laser & Optoelectronics Progress
- Publication Date: Mar. 10, 2024
- Vol. 61, Issue 5, 0522002 (2024)
Bionic Compound Eye Based on a Flexible Fresnel Lens Array
Wenya Zhao, Yecan Zhang, Yonghao Jiao, Haobo Sun, Ningde Miao, Dongdong Han, and Yonglai Zhang
Biological compound eyes have excellent optical properties, including large field of view, small size, no aberrations, and sensitivity to moving objects. Sensitivity to moving objects is crucial for flying insects that chase small, fast-moving targets. Inspired by the sensitivity of compound eyes possessed by insects to moving objects, we prepared a single-layer bionic compound eye with five ommatidia, each consisting of a Fresnel lens. Using femtosecond laser two-photon polymerization processing technology and soft lithography technology, a flexible bionic compound eye with high accuracy and repeatability was prepared. Experimental results show that the prepared bionic compound eye could obtain high-quality images and be used to track moving targets. Biological compound eyes have excellent optical properties, including large field of view, small size, no aberrations, and sensitivity to moving objects. Sensitivity to moving objects is crucial for flying insects that chase small, fast-moving targets. Inspired by the sensitivity of compound eyes possessed by insects to moving objects, we prepared a single-layer bionic compound eye with five ommatidia, each consisting of a Fresnel lens. Using femtosecond laser two-photon polymerization processing technology and soft lithography technology, a flexible bionic compound eye with high accuracy and repeatability was prepared. Experimental results show that the prepared bionic compound eye could obtain high-quality images and be used to track moving targets.
Laser & Optoelectronics Progress
- Publication Date: Mar. 10, 2024
- Vol. 61, Issue 5, 0522001 (2024)
Error Calibration Method of Null Correctors for Large-Aperture Aspherical Mirrors
Qiuyun Xu, and Lingchen Kong
Aspheric mirrors commonly utilize a zero position compensator along with an interferometer for surface shape detection. Therefore, the machining and assembly accuracy of the zero position compensator play a crucial role in determining the reliability of the detection results. This paper introduces a universal compensation error calibration method based on computer generated hologram (CGH). To test the method, a Φ856 mm,f/1.54 hyperboloid mirror is employed as the target aspheric mirror. First, a reflective CGH is designed, and the phase function of the CGH is determined using a ray tracing method. This ensures that the introduced spherical aberration is the same as the normal aberration of the aspheric main mirror to be tested. Subsequently, the correctness of the design is confirmed through ZEMAX simulation calculation, and the primary hologram is processed based on the phase function. Holographic strips are designed and processed on the same glass substrate for adjusting the calibration optical path. The experimental results demonstrate that the CGH calibration achieves a zero position compensator accuracy of λ/80. The proposed method is applicable to concave aspheric mirrors with large apertures and fast focal ratios. Consequently, it can serve as a reliable guide for calibrating zero position compensators in most positive axis aspheric mirrors. Aspheric mirrors commonly utilize a zero position compensator along with an interferometer for surface shape detection. Therefore, the machining and assembly accuracy of the zero position compensator play a crucial role in determining the reliability of the detection results. This paper introduces a universal compensation error calibration method based on computer generated hologram (CGH). To test the method, a Φ856 mm,f/1.54 hyperboloid mirror is employed as the target aspheric mirror. First, a reflective CGH is designed, and the phase function of the CGH is determined using a ray tracing method. This ensures that the introduced spherical aberration is the same as the normal aberration of the aspheric main mirror to be tested. Subsequently, the correctness of the design is confirmed through ZEMAX simulation calculation, and the primary hologram is processed based on the phase function. Holographic strips are designed and processed on the same glass substrate for adjusting the calibration optical path. The experimental results demonstrate that the CGH calibration achieves a zero position compensator accuracy of λ/80. The proposed method is applicable to concave aspheric mirrors with large apertures and fast focal ratios. Consequently, it can serve as a reliable guide for calibrating zero position compensators in most positive axis aspheric mirrors.
Laser & Optoelectronics Progress
- Publication Date: Feb. 25, 2024
- Vol. 61, Issue 4, 0422001 (2024)
Design of a Compact Infrared Continuous Optical Zoom System Based on Alvarez Lenses
Qi Ouyang, Mengyao Liu, Yan Ning, Jie Cao, Qun Hao, and Yang Cheng
In this study, a transverse moving infrared optical continuous zoom system based on the Alvarez lens is proposed to address the challenges associated with the complex structure and large volume of traditional axial-moving mechanical optical zoom systems. The system consists of two sets of Alvarez lenses, apertures, focusing lenses, and infrared detectors. Herein, two sets of Alvarez lenses adopt a Kepler-type telescope structure, where the first set of Alvarez lenses functions as the zoom group and the second set of Alvarez lenses serves as the compensation group. The infinitely far incident light passes through two sets of Alvarez lenses and exits, the emitted parallel light is then focused and imaged onto the target surface of the infrared detector through a fixed focal lens. Utilizing Zemax software for optical simulation, our designed optical zoom system covers the 8?12 μm long wave infrared band, with a maximum field of view angle of 6°, a maximum pupil diameter of 6 mm, an F-number of 2, distortion of <2.1%, and a total optical length of ~74 mm. The Alvarez lens only requires to be horizontally moved by ~1 mm to achieve continuous optical magnification from 5× to 15×. Moreover, the modulation transfer function of the proposed optical zoom system can attain up to 0.5@17 lp/mm, assuming a resolution of 320×240 and pixel sizes of 30 μm for the infrared detector. The simulation results indicate that the system has the advantages of high magnification, a compact structure, and high imaging quality, making it a promising candidate for applications in the field of miniaturized infrared zoom imaging. In this study, a transverse moving infrared optical continuous zoom system based on the Alvarez lens is proposed to address the challenges associated with the complex structure and large volume of traditional axial-moving mechanical optical zoom systems. The system consists of two sets of Alvarez lenses, apertures, focusing lenses, and infrared detectors. Herein, two sets of Alvarez lenses adopt a Kepler-type telescope structure, where the first set of Alvarez lenses functions as the zoom group and the second set of Alvarez lenses serves as the compensation group. The infinitely far incident light passes through two sets of Alvarez lenses and exits, the emitted parallel light is then focused and imaged onto the target surface of the infrared detector through a fixed focal lens. Utilizing Zemax software for optical simulation, our designed optical zoom system covers the 8?12 μm long wave infrared band, with a maximum field of view angle of 6°, a maximum pupil diameter of 6 mm, an F-number of 2, distortion of <2.1%, and a total optical length of ~74 mm. The Alvarez lens only requires to be horizontally moved by ~1 mm to achieve continuous optical magnification from 5× to 15×. Moreover, the modulation transfer function of the proposed optical zoom system can attain up to 0.5@17 lp/mm, assuming a resolution of 320×240 and pixel sizes of 30 μm for the infrared detector. The simulation results indicate that the system has the advantages of high magnification, a compact structure, and high imaging quality, making it a promising candidate for applications in the field of miniaturized infrared zoom imaging.
Laser & Optoelectronics Progress
- Publication Date: May. 25, 2024
- Vol. 61, Issue 10, 1022001 (2024)
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