| 宽光谱可见-短波红外成像光学系统设计 |
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| 引用本文： | 宣斌,赵泽宇,罗曜伟,魏群,朱倚娴,王亚军.宽光谱可见-短波红外成像光学系统设计[J].红外与激光工程,2023,52(4):20220638-1-20220638-8. |
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| 作者姓名： | 宣斌 赵泽宇 罗曜伟 魏群 朱倚娴 王亚军 |
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| 作者单位： | 1.南通大学 机械工程学院，江苏 南通 226019 |
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| 基金项目： | 国家自然科学基金（61903204） |
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| 摘 要： | 针对目前的红外成像光学系统在机器视觉工业检测领域难以同时实现成像质量好和结构紧凑设计的问题，提出了一种宽光谱可见-短波红外成像光学系统的设计方法。运用光学设计软件ZEMAX设计了一种适用于可见光和短波红外的红外成像光学系统。该系统由7组10片透镜组成，利用多组双胶合透镜来消色差，在第15个面使用非球面提高成像质量，最后对系统的成像质量进行研究。设计结果表明：该系统的的工作波长为0.4～1.7μm，全长为79.6 mm,F数为2.8，焦距为25.7 mm，畸变小于1.4%，调制传递函数值在奈奎斯特频率100 lp/mm处均大于0.4，接近衍射极限，成像质量良好。该系统可以对光滑表面的装配件进行缺陷检测，具有结构简单、易于加工装调的优点，有助于高效地完成机器视觉检测。
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| 关 键 词： | 宽谱段 光学设计 可见光成像 红外成像 机器视觉 |
| 收稿时间： | 2022-09-08 |
Design of optical system for wide-spectrum visible-short wave infrared imaging |
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| Affiliation: | 1.School of Mechanical Engineering, Nantong University, Nantong 226019, China2.Faculty of Electronic and Information Engineering, Xi'an Jiaotong University, Xi'an 710049, China3.Nanjing Huaopt Technology CO. LTD, Nanjing 210000, China4.Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi'an 710119, China |
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| Abstract: | Objective The industrial lens for machine vision inspection needs not only to meet the design requirements of lightweight and large field of view, but also have high luminous flux. In this paper, based on the needs of machine vision engineering applications, an optical system for wide-spectrum visible-short wave infrared imaging is designed using the optical design software ZEMAX. The Wide spectrum visible-short wave infrared imaging system can operate in the band of 0.4-1.7 μm. The system is composed of 7 groups of 10 lenses. The MTF value is greater than 0.4 at the Nyquist frequency of 100 lp/mm. The F number of the system is 2.8, and the distortion is less than 1.4%. All kinds of aberrations have been well corrected and balanced. And the system has good imaging performance. It has certain reference value for the design of similar optical systems. Methods The optical system structures are usually divided into refractive system, reflective system and hybrid system. Different optical system structures have their own advantages and disadvantages. According to the imaging performance of the system and the cost-performance ratio in industrial applications, the refractive system can meet the requirements of large field of view, low distortion and compact structure. The refractive system is used to observe through refraction of transmitted light, so it is widely used in optical structure selection. At the time, by using the conventional processing and adjustment methods, it can meet the accuracy requirements. It has the characteristics of stable image quality, small stray light and high element transmittance. Results and Discussions According to the actual needs of industrial testing, the main parameters to be considered in the structural design of the wide-spectrum visible-short wave infrared imaging optical system are lens material, working band, focal length, F number, field angle, total length of the system, etc. Based on the analysis of the parameters of the wide-band infrared imaging system, the resolution CMOS area array detector is 2448×2048. The pixel size is 3.45 μm. The target size is 2/3 inch (1 inch=2.54 cm), and the lens has stable optical performance and good imaging quality in the operating temperature range of 0-50 ℃. After the initial structure of the system is determined, the design structure is further optimized using subsequent repeated aberration correction. The optimized wide-spectrum visible-short wave infrared imaging optical system is composed of 7 groups of lenses, and the number of the lenses is 10. The diaphragm is located on the rear surface of the fourth lens, and the front surface of the tenth lens is aspheric. The total length of the system is 79.6 mm, the diameter of the entrance pupil is 9.9 mm, and the F-number is 2.8. It can image in the visible light and short-wave infrared bands. After testing, the point array of the system's field of view is very close to the Airy spot, which is close to the diffraction limit, and meets the imaging requirements. The maximum astigmatism and field curvature of the system is 0.1 mm, and the maximum distortion is 1.4%, which meets the requirements of the system design for field curvature and distortion. The systematic tolerance is analysed based on diffraction MTF average. According to the experience and actual technological level, firstly, relatively loose tolerance preset value of each parameter is given, and then the tolerance analysis is carried out based on the design results, finally the particularly sensitive tolerance is found out and the tolerance is reallocated. Through Monte Carlo analysis of MTF, the results show that at 100 lp/mm, the nominal value of MTF is 0.559, the best value is 0.554, the worst value is 0.333, the average value is 0.481, and the standard deviation is 0.052, the MTF of 90% of the lens≥ 0.410, the MTF of 50% of the lens ≥ 0.427, and the MTF of 10% of the lens≥ 0.540. Based on the results, the MTF can meet the technical index requirements under the given tolerance. In order to better prove the performance of the optical system, the bruises in the interior of agricultural products are taken with a visible light band camera and a short-wave infrared camera respectively, which proved that the bruises can be clearly seen in the object image of this wavelength by SWIR imaging. The ability of SWIR to penetrate plastic was proved by shooting through plastic bottles. The experiment proves that the system has good detection effect in industrial detection. Conclusions With the increasing demand of machine vision for composite image information, the modern optical imaging technology will expand beyond the visible and near-infrared bands. Short-wave infrared will be more widely used in the future because of its resolution comparable to visible light and unique optical performance. |
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