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为解决航空遥感相机检焦系统故障分析、元器件选型及提高检焦精度的问题,本文深入研究了基于Ronchi光栅的光电自准直检焦法。首先,归纳总结了国内外航空相机常用的几种检焦方法,对比了每种检焦方法的优缺点。接着,重点介绍了基于Ronchi光栅的光电自准直检焦系统的构成和工作原理,建立了数学模型,模拟了检焦系统在不同像面位置处的输出波形。然后,为衡量离焦程度,提出了离焦评价因子的概念,接着分析了光学系统的衍射效应和像差大小、Ronchi光栅的周期选择及检焦光源的能量分布这三种因素对检焦精度的影响,给出了Ronchi光栅周期的选择方法。最后,通过实验的方法对本文的仿真结果加以验证。实验结果表明:合焦波形的峰峰值占比0.82,对应0.05 mm步长下的平均检焦分辨力约为10%。 相似文献
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In this paper,the waveforms in time domain and frequency domain of two kinds of optical frequency domain reflectometry (OFDR) sensing systems are compared,which use common fiber Bragg grating (FBG) and... 相似文献
125.
《Journal of Materials Processing Technology》2014,214(4):839-843
On-line monitoring of an arc-welding process is performed in this paper by means of fiber Bragg grating transducers (FBGs) in two different configurations. FBGs were glued to the plate surfaces next to the weld joint, and a FBG transducer was designed to sense the perturbations in the air surrounding the welding plasma column. Sensitivity to both temperature and vibrations during the process was analyzed during several tungsten inert gas (TIG) welding tests, showing the feasibility of the proposed design to perform an on-line detection of different welding perturbations. To enhance the analysis, a setup based on plasma optical spectroscopy was also employed to allow a comparison among the response of both techniques to the appearance of these perturbations. 相似文献
126.
A new structure for the L-band multiwavelength switchable erbium-doped fiber laser is proposed. Overlapping laser cavities are formed by cascading fiber Bragg gratings as reflectors in a ring structure with a C-band EDFA as a common gain medium. The proposed laser is made to be wavelength-switchable by individually adjusting the loss of each overlapping cavity. Instead of using an L-band EDFA as the gain medium in the L-band fiber laser, we have experimentally demonstrated that by tailoring the gain of the C-band EDFA to have a significant gain tilt in the L-band, a lasing power efficiency of 26% can be achieved over a wide range of switchable lasing wavelengths. Following this optimal design, the side-mode suppression ratio and the minimal separation between two switchable lasing wavelengths were found to be over 42 dB and 0.33 nm, respectively. 相似文献
127.
Traditional metallic gratings and novel metamaterials are two basic kinds of candidates for perfect absorption. Comparatively speaking, metallic grating is the preferred choice for the same absorption effect because it is structurally simpler and more convenient to fabricate. However, to date, most of the perfect absorption effects achieved based on metamaterials are also available using an metallic grating except the tunable dual(multi)-band perfect absorption. To fill this gap, in this paper, by adding subgrooves on the rear surface as well as inside the grating slits to a free-standing metallic grating, tunable dual-band perfect absorption is also obtained for the first time. The grooves inside the slits is to tune the frequency of the Cavity Mode(CM) resonance which enhances the transmission and suppresses the reflectance simultaneously. The grooves on the rear surface give rise to the phase resonance which not only suppresses the transmission but also reinforces the reflectance depression effect. Thus, when the phase resonance and the frequency tunable CM resonance occur together, transmission and reflection can be suppressed simultaneously, dual-band nearly perfect absorption with tunable frequencies is obtained. To our knowledge, this perfect absorption phenomenon is achieved for the first time in a designed metallic grating structure. 相似文献
128.
等效相移光栅的原理是,通过对取样光纤布拉格光栅在特定点进行毫米尺度的“位移”,经过傅里叶变换,在各频率通道产生“等效相移”。首先利用光栅的Turan传输矩阵进行数值模拟,验证了真实相移光栅的各种性质在等效相移光栅中的实现,然后针对当前关于等效相移光栅的报道中,-2级光栅反射率都很低,并且没有出现“等效相移”的情况,提出了一种实现-2级等效相移光栅的方法,并进行了仿真验证。最后给出了等效相移光栅反射率随长度变化的曲线。 相似文献
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在分析光谱测试仪器检测设备发展现状的前提下,为解决光栅分辨率测试仪器中存在的电路复杂、探测器灵敏度低、结构可变通性差等问题,设计了一种以线阵CCD ILX554B为探测器的、以STM32F103为主控单元的线阵CCD光谱分辨率检测系统。系统利用片上高速时钟产生线阵CCD所需的驱动时序,经片上ADC采样后获取实时的光谱数据,将采集的数据经USB接口上传给上位机进行处理,获得最终的被测分光器件的光谱分辨率信息。最后,分别以汞灯和氩灯为光源,利用所设计的系统对光栅分辨率进行了测试,实验数据表明,在500 k Hz的驱动频率下,系统光谱分辨率可以达到0.01nm。系统满足低成本、高精度、稳定和可靠等要求。 相似文献