Optical Design and Fabrication|20 Article(s)
Study on Bessel Lens for Picosecond Laser Cutting
Zhang-fan WEI, Chuan SUN, Kai GUO, Ming CHEN, Li-hua HUANG, Ai-jun ZENG, and Hui-jie HUANG
A Bessel lens for laser cutting and beam measurement system are designed and developed. Additionally, picosecond Bessel beam is generated by a picosecond pulse laser and the designed Bessel lens, and it is used for the cutting experiment on a piece of silicate glass with the thickness of 1 mm. The results show that, by the incidence of a Gaussian beam with certain diameter on the Bessel lens, the central core diameter and non-diffracting propagation distance of the generated Bessel beam are 3.4 μm and 2.46 mm, respectively. In the cutting experiment, the diameters of the surface micro-holes before glass breaking are smaller than the designed central core diameter of Bessel beam. The designed Bessel lens and beam measurement system in this paper can satisfy the application requirements of laser cutting.
Acta Photonica Sinica
  • Publication Date: Oct. 15, 2020
  • Vol. 49, Issue 10, 1022001 (2020)
An X-ray Detection Technology with Multi-curvature Bent Crystal
Jun SHI, Miao LI, Lin-dong-ying LUO, Feng WANG, Guo-hong YANG, and Min-xi WEI
In the spectrum diagnostic physics experiment of inertial confinement fusion, the spectral signal is weak due to the X-ray diffraction efficiency with crystal. So a spectral diagnostic instrument with high light collection efficiency and wide spectral range is urgently needed. A multi-curvature bent crystal multi-energy point imaging technique is proposed based on traditional conical crystal structure. It has the characteristics of wide spectral range, strong focusing ability and high spectral resolution. At the same time, it can eliminate imaging aberration in principle due to the rotational symmetry of imaging light. The measuring spectra experiment of multi-curvature bent α-quartz crystal is conducted at a Ti X-ray tube device and the same experiment with plane α-quartz crystal is done to demonstrate the strong focusing ability. The result shows that the intensity of multi-curvature bent α-quartz crystal is 100 times than that of plane crystal, and the energy range of detected X-ray is 4.51~5.14 keV. This device combined with a streak camera at a vertical direction could be used to collect weak X-ray with wide spectral range.
Acta Photonica Sinica
  • Publication Date: Mar. 25, 2020
  • Vol. 49, Issue 3, 0322001 (2020)
Design and Test of Thermo Electric Cooling System for Space Based Telescope Detector Assembly
Wen-gang YANG, Xue-wu FAN, Chen-jie WANG, De-jin QIN, Bao-peng LI, Yun-fei DU, Liang-jie FENG, Hui ZHAO, and Wei GAO
Active cooling must be utilized to meet the need for the space-based telescope which need very low detector noise level. The precise thermal control measures based on thermo-electric cooling technique are utilized and especially the package system and heat rejection system of thermo-electric coolers and its cotroller system are designed respectively. The parasitic heat load to the detector and the heat path resistances are optimized to reduce the input power and the radiator size. Based on the Peltier effect and Joule effect and Frourie effect, the relations between the enviroments parameters and working parameters are analyzed. The enviroments parameters include the heat pumped requirements, the thermal resistance between the hot side and the sink and the hot side sink temperature, while the working parameters include the current, voltage and input power of coolers. The sensitivity between the heat loads, thermal resistance and the input power are especially researched. The qualification model of the telescope is developed and the thermal vaccum and balance test are accomplished. The test results show that the system design are appropriate and effective, the detector temperature is controlled at -75±0.2℃. Based on the test environments conditions and the cooler's working parameters, the thermal analysis model are discussed and corrected.These lessons can provide some reference for the development of thermo-electric cooling system of the similar space based telescope.
Acta Photonica Sinica
  • Publication Date: Aug. 01, 2020
  • Vol. 49, Issue 8, 0822001 (2020)
Optical System Design of Miniaturized Fundus Camera Based on Non-coaxial Array Illumination
Yan-xiong WU, Zhi-yuan GUO, Miao YU, and Li-ping WANG
The mathematical model of fundus imaging under the non-coaxial array illumination is established. A micro optical system of fundus camera is proposed by using the independent design method of illumination light path and imaging light path, which avoids the interference of human cornea and omental objective reflected light on the retina image in the traditional fundus camera. The design of 6-array ring light source illumination system is completed, which is only 17.9 mm in length and the effective illumination line field of fundus retina is not less than 12 mm. The secondary imaging design is adopted in the imaging optical system.The modulation transfer function is better than 0.2@91 lp/mm and the distortion is less than 5% with 75 mm length. The simulation and design results show that the optical system of the proposed fundus camera can effectively suppress the stray light in the optical path which is conducive to obtaining high contrast retinal image. The results can provide a design reference for the development of high image quality, miniaturization and low stray light fundus camera.
Acta Photonica Sinica
  • Publication Date: Aug. 01, 2020
  • Vol. 49, Issue 8, 0822002 (2020)
Manufacturing of Infrared Polarization Imaging Optical System Based on Micro-scanning
Chen TIAN, Peng CHEN, Xiaojie ZHANG, Huabao LONG, Mingyang HOU, and Zhengxiang SHEN
Division of focal plane polarimeters can obtain transient polarization imaging information, which is a research hotspot in the field of infrared polarization imaging technology. However, there are also some shortcomings. In the measurement process, the instantaneous field of view error will be produced and the image resolution will be reduced. The method of combining micro-scanning technology and infrared polarization imaging technology can make up for the above shortcomings. The focusing lens in the infrared imaging system is used as the micro-scanning lens and fixed on the two-dimensional micro-scanning platform which adopts 2×2 mode to implement periodic scanning. Finally, four sequential images of the same scene with one pixel shift can be obtained, to obtain the target's polarized light intensity data in 4 different directions, and then calculate the Stokes parameters. The polarization imaging optical system based on lens micro-scanning requires that the displacement of the micro-scanning lens does not reduce the imaging quality, that is, the tolerances such as the coaxiality, true position, and scanning displacement of the micro-scanning lens are not sensitive, so higher requirements are proposed for the design and assembly of the optical system.The article first discusses the relevant theoretical basis of polarization based on Stokes vector method, introduces the representation of Stokes vector and the calculation formulas of polarization degree and polarization angle, and then introduces the division of focal plane polarimeters based on micro-scanning technology in detail, including the distance of each displacement, the movement path of the micro-scanning lens.What's more, the infrared imaging system is designed. The catadioptric system is selected as the initial structure, the aspherical secondary mirror is simplified to a plane mirror only for reflecting the light path, and then the aspherical rear lens group is used to correct the aberration. The infrared system has four lenses, and using the last lens as a micro-scanning lens to realize the orthogonal displacement of 2×2 mode. The wavelength of the system is 3~5 μm, the F-number is 2, the optical field angle is ±2°, the focal length is 176 mm and the aperture is not less than φ40 mm. After completing the optical design, the optical transfer function and spot diagram are performed. The optical transfer function of each field is higher than 0.47@17 lp/mm and the RMS radius of each field is less than 11 μm. The results show that the optical system meets the requirements for use. Then the tolerance analysis is completed. From the result of the Ment-Karol simulation, the probability of MTF value greater than 0.2@17 lp/mm is over 90%. The influence of the coaxiality, true position, and scanning displacement of the micro-scanning lens on the imaging quality is also analyzed. The system MTF value changes with the decenter and tilt of the micro-scanning lens in the X and Y directions are provided. The results show that the optical system can still ensure good imaging quality in the range of decenter ±200 μm and tilt ±0.4°, and it is not sensitive to tolerances. In addition, structural design is completed. The entire imaging system includes the optical system and the mechanical structure supporting the optical system. Among them, the support frame is made of titanium alloy material to improve rigidity and the rest of the structure is made of aluminum alloy material. The main reflector is the core of the catadioptric optical system, and its surface shape accuracy determines the imaging quality of the system. Therefore, a stress isolation groove is used to realize a flexible connection with the support frame. All mirrors and lenses are machined using a single point diamond turning method.Finally, a polarization imaging experiment is carried out with the developed system, and the results show that infrared polarization imaging images have higher contrast, clearer target contours, and better identification of different materials compared with infrared intensity imaging.
Acta Photonica Sinica
  • Publication Date: Jun. 25, 2022
  • Vol. 51, Issue 6, 0622001 (2022)
Design Method of Solar Radiation Simulation Optical System with High Energy Utilization Rate
Fanlin MENG, Shi SU, Guoyu ZHANG, Jian ZHANG, Shi LIU, Gaofei SUN, and Haowen PENG
Aiming at the disadvantages of large-scale solar simulators in the past, such as complex structure, low energy utilization rate and poor uniformity, a design method of solar radiation simulation optical system with high energy utilization rate was proposed. The ellipsoid condenser was designed based on the luminous characteristics of the real xenon lamp. By adding a spherical reflector, the combined condenser system was used to improve the energy utilization rate. The optical integrator was designed according to the principle of pupil matching. The irradiation uniformity was improved by the edge elimination method. The simulation results suggest that the energy utilization rate of the combined condenser system is 21.2% higher than that of the single ellipsoid condenser. The irradiation uniformity of the edge elimination method is 4% higher than that of the edge compensation method. The experimental results suggest that the working distance is 20 m, irradiation surface diameter is Φ2 m, maximum irradiance is 1 363.1 W·m-2, non-uniformity is ±4.5%. It has realized large-area, high-energy utilization rate solar radiation simulation, which provided an advanced means for semi-physical simulation and testing of solar sensors in space field.
Acta Photonica Sinica
  • Publication Date: Dec. 25, 2021
  • Vol. 50, Issue 12, 1222003 (2021)
Optical Design and Tolerance Analysis of Freeform Automotive Head-up Display
Yang-liu ZHANG, Zhou-ping SU, Hong-xiang PAN, Xing-tao CHEN, and Wen-yu ZHANG
A freeform optical system of automotive Head-Up Display (HUD) was designed. In the initial layout design of the HUD optical system, the sample points on two optical freeform surfaces of the HUD optical system are calculated by the seed curve extension algorithm. And the two freeform surfaces are expressed by the extended polynomials. Then the ray tracing is performed for the initial layout of the HUD optical system at center field of view with 0.5 mm ray sampling interval. The results show that the performance of the initial layout of the HUD optical system is the diffraction-limited, which can be used as the starting point for further optimization at full field of view. After optimization, the final HUD optical system is obtained. In order to simulate the observation of human eyes, several test points in the Eyebox are taken as object points, which are imaged on the image plane by the HUD optical system. The modulation transfer function plots of the several test points are greater than 0.5 at 6 lp/mm, which are close to diffraction limit. And the distortions of the final HUD system are less than 2%. Finally, the manufacture tolerances of two optical freeform surfaces are analyzed. The results show that the modulation transfer function plots of the HUD optical system are higher than 0.3 with the tolerance PV values of 0.42 μm and 0.62 μm of the two optical freeform surfaces respectively. For the current machining capacity, the tolerance requirements are reasonable.
Acta Photonica Sinica
  • Publication Date: Sep. 01, 2020
  • Vol. 49, Issue 9, 0922002 (2020)
Optimization Design of Illumination Uniformity of Relay Lens in Lithography Illumination System
Shuang GONG, Baoxi YANG, and Huijie HUANG
Lithographic apparatus is widely recognized as an efficient tool in manufacturing Integrated Circuits (ICs) and other micro–nano structures. During the manufacturing process of ICs, the exposure field is scanned by a narrower illumination field. Illumination uniformity is a key factor in determining resolution and Critical Dimension Uniformity (CDU), which are important performance parameters in advanced lithography systems. To obtain higher photolithography resolution and better CDU, the exposure dose must be kept as uniform as possible in the cross-scanning direction. Improving the consistency of the numerical aperture of each field of relay lens is the premise of ensuring the illumination uniformity. In the optimization conventional imaging optical design, wavefront error, dispersed spot, or optical transfer functions are generally employed as evaluation functions. Therefore, it is impossible to fully and completely satisfying the performance evaluation requirements of the relay lens group using the traditional aberration evaluation method. The general illuminance calculation of the optical system is based on the Monte Carlo method. The computational accuracy degree of the result is related to the number of traces light. In the mainstream optical design software, it is used in a calculation method of four-square cosine of the field angle, in a large number of engineering practice, the difference between the expected illumination distribution of the algorithm and the actual distribution are large. Especially for the telecentric optical system, the result of this calculation method is very worth to be suspected. The relay lens group is used to image the illumination field on the scanning slit plane on the mask plane. The relay lens group has a feature of double telecentric and adjustable pupil, so the above algorithm is still not suitable for the relative illuminance calculation of the image plane of the relay lens group. In this paper, a fast algorithm for calculating the uniformity of illumination is proposed, in which the numerical aperture of the system is calculated by approximate algorithm, and the illumination is characterized by the numerical aperture of exit pupil. The non-uniformity of light field is calculated by this algorithm, which is used as the evaluation function in the process of automatic optimization to optimize the design of relay lens of lithography illumination system. Then the designed relay lens is simulated by the software Light tools. The simulation results show that the non-uniformity of the illumination on the mask surface is less than 0.5% under different coherence factors. Simulation shows that the algorithm results have high correlation with the actual performance, reflecting the actual illumination uniformity, and can improve the uniformity of the system by controlling the value of the evaluation function. The result of the algorithm is proved to have a conservative characteristic, that is, the actual illumination uniformity will exceed the design value, which ensures that the obtained results meet the performance requirements. And this evaluation algorithm has a huge advantage in the speed, which can meet the needs of optimized design. Finally, the integral uniformity of the designed relay lens is tested through experiment, and the results shown that the non-uniformity of illumination is less than 1.21%, which can meet the requirement of the illumination non-uniformity on the mask surface (< 1.5%). It is proved that the fast evaluation algorithm is effective in the optimal design of relay lens.
Acta Photonica Sinica
  • Publication Date: Mar. 25, 2022
  • Vol. 51, Issue 3, 0322001 (2022)
Multi-axis Focusing Lens Design for Precise Assembly of High-resolution Mobile Phone Lens
Fanghan CHEN, Guangyu ZHAO, Xiaomei ZHANG, Shilong JIANG, and Zhigang WEN
In the manufacturing process of high-resolution mobile phone lens consisted of glass and plastic material, many problems of assembly between glass lens and plastic lens group were existed such as sensitive to position change, low efficiency and low yield. The optimal proposal based on multi-point infinite conjugation modulation transfer function measurement was adopted to lens alignment and assembly in real-time feedback. As a critical imaging component of chart acquisition for modulation transfer function calculation, performance of multi-axis focusing lens played a significant role in guaranteeing measurement accuracy. The relationship between the design parameters of multi-axis focusing lens and the optical parameters of mobile phone lens to be assembled was established. Multi-configuration setting and aberration optimization of multi-axis focusing optical system were realized by ZEMAX simulation software. Simulation results showed that the size of focusing lens was compact, and both its tangential and sagittal modulation transfer function curves were nearly coincided with diffraction limit. The designed multi-axis focusing lens theoretically could be flexibly exploited to multi-point modulation transfer function measurement and precise assembly of high-resolution mobile phone lens up to 48 megapixel, which maximum full field of view angle reached 106°.
Acta Photonica Sinica
  • Publication Date: Dec. 25, 2021
  • Vol. 50, Issue 12, 1222001 (2021)