分类： 光学 >> X 射线光学器件 提交时间： 2025-03-02
摘要： Ghost imaging (GI), as a novel imaging technique, facilitates image acquisition under low light conditions through single pixel measurements, thus holding great potential in various application areas ranging from biomedical imaging, remote sensing imaging, biometrics, astronomy to 3D imaging. However, to reconstruct high resolution images, GI typically requires a large number of single pixel samplings, which is extremely time consuming and poses practical limitations to its applications. Parallel ghost imaging treats each pixel of the position sensitive detector as a bucket detector and simultaneously performs tens of thousands of ghost imaging in parallel. In previous work, we gradually achieved parallel ghost imaging with high pixel resolution, low dose, and ultra large field of view. Parallel ghost imaging has demonstrated excellent performance and great potential. All this is so exciting. But since all our experiments were carried out at synchrotron radiation facilities, with a series of almost luxurious conditions such as nearly infinite and continuous light supply time, monochromatic, pure, and energy adjustable X rays, expensive and precise experimental equipment, and complete supporting facilities, many peers lacking experimental conditions cannot replicate parallel ghost imaging. Meanwhile, the high cost also hinders its cross field integration. Furthermore, we got rid of the synchrotron radiation source and completed the pipeline style acquisition of parallel ghost imaging in a way that uses rough and inexpensive equipment and is most imitable by others. We achieved high quality ghost imaging with an effective pixel size of 8.03 \textmu m and an image size of 2880×2280 at a laboratory X ray source. The total cost of transforming an X ray computed tomography device into a parallel ghost imaging experimental platform is only $40. Parallel ghost imaging has been generalized from synchrotron radiation sources to X ray tubes.However, a key problem remains unsolved. The object arm signal on our laboratory light source was obtained through artificial fitting, and the true magnification relationship between the reference arm and the object arm has not been established. In synchrotron radiation, we achieved true magnification using different magnifying optical lens groups. On the one hand, such a set of lenses is very expensive, making the generalization of parallel ghost imaging difficult again. On the other hand, the flux of the X ray tube is very small, which leads to extremely low efficiency. In this work, we find that compared with the parallel beam of synchrotron radiation, the cone beam of the X ray tube naturally has the characteristic of true magnification by gradually moving the detector away from the light outlet. We only use one detector. When collecting the object arm signal, the detector is moved to a position 30 cm away from the light outlet, and when collecting the reference arm signal, the detector is moved to a position 150 cm away from the light outlet. These two positions form a true magnification relationship of 5 times, achieving super resolution of parallel ghost imaging on the X ray tube. A series of high quality ghost imaging results with an effective pixel size of 7.095 \textmu m and an image size of 2880×2280 in pipeline style acquisition were obtained. The realization of true magnification based on the X ray tube is a prerequisite for achieving ultra large field of view and low dose imaging. Completing this work at zero cost implies great application value and commercial potential.
分类： 化学 >> 分析化学 分类： 农、林、牧、渔 >> 农产品贮藏与加工 分类： 光学 >> 光谱学 分类： 食品科学技术 >> 食品包装与储藏 提交时间： 2024-12-24
摘要： 香榧陈籽由于储存期间不饱和脂肪酸氧化，导致其口感降低，品质变差。不法商人为谋取暴利，将香榧陈籽掺入新籽售卖，侵害消费者利益，需要一种快速无损鉴别方法。方法：本研究利用近红外光谱技术对香榧陈籽进行快速无损判别研究。采用两种近红外光谱仪在200-1160nm及900-1700nm波段范围内采集带壳香榧样本的光谱，使用9种方法对光谱数据进行预处理，然后利用区间优化选择算法（ICO）、竞争自适应重加权采样（CARS）、连续投影算法（SPA）和变量组合种群分析(VCPA）四种波长选择方法筛选香榧陈籽的光谱特征变量，并应用线性判别分析（LDA）、支持向量机（SVM）、反向神经网络（BP）方法建立香榧陈籽的判别模型。结果：对于光谱仪1，CARS方法为最优的波长选择方法，CARS-SVM模型的性能最优，其预测集的敏感性、特异性和准确率均为100%。对于光谱仪2，标准化和SNV为较优的预处理方法，VCPA变量选择方法优于其它三种方法，所建立的最优模型为VCPA-BP，其模型的预测集敏感性、特异性和准确率分别为98.18%、93.02%、和95.04%。结论：由此可知，两光谱仪数据建立的判别模型均能较好地实现香榧陈籽的判别，光谱仪1的模型总体上性能优于光谱仪2。本研究可为香榧陈籽快速无损判别提供一种检测方法，有效保障香榧的品质。
分类： 光学 >> 其他光学领域 提交时间： 2024-08-26
摘要： Based on the Global Positioning System (GPS) range measurement equation whose correctness has been fully proven by GPS practices, we found that in an inertial system which is moving relative to the Earth Centered Inertial (ECI) frame, the propagation speed of light is neither constant nor isotropic, but , where v is the velocity of the system relative to the ECI frame and is the unit vector of the direction of light propagation. Utilizing an interferometer of two independent ultrastable lasers, a crucial experiment examining this important scientific problem with a low translational speed of the interferometer is proposed; and its comparison with an existing experiment of the generalized Sagnac effect is also presented. Besides, such an interferometer can be utilized to examine another important scientific problem: whether the speed of light is isotropic or not on rotating Earth’s surface. Because the vast majority of optical laboratories on the surface of the Earth have high linear velocities of the Earth’s rotation, only a small change of the orientation of the interferometer is sufficient.
分类： 光学 >> 光纤和光通信 分类： 电子与通信技术 >> 光电子学与激光技术 提交时间： 2024-08-17
摘要： Optical neural networks have long cast researchers’attention nowadays. Like other optical structured neural networks, fiber neural networks which utilize the mechanism of light transmission to compute can take great advantages in both computing efficiency and power cost. Though the potential ability of optical fiber was demonstrated via the establishing of fiber neural networks, it will be of great significance of combining both fiber’s transmission and computing functions so as to cater the needs of future beyond 5G intelligent communication signal processing. Thus, in this letter, the fiber neural networks and their related optical signal processing methods will be both developed. In this way, information derived from the transmitted signals can be directly processed in the optical domain rather than being converted to the electronic domain. As a result, both prominent gains in processing efficiency and power cost can be further obtained. The fidelity of the whole structure and related methods is demonstrated by the task of modulation format recognition which plays important role in today’s fiber optical communications without losing the generality.
分类： 光学 >> 超快光学元件 提交时间： 2024-01-31
摘要： 对基于压缩感知和条纹相机的压缩超快成像系统进行了模拟仿真， 原始三维图像I（x-y-t） 经数字微镜设备（digital micromirror devices, DMD） 进行编码调制， 然后传输至狭缝全开条纹变像管， 经偏转电场作用后， 多幅不同时间图像将叠加， 并在 CCD 上输出最后积分图像。 采用总变分还原算法将 CCD 积分图像重构出多幅原始图像 I（x-y-t） 。 对压缩超快成像系统的图像采集过程及还原算法进行了模拟仿真， 获得了激光在空气介质中传输过程的 8 幅动态二维图像， 每幅图像的曝光时间为 12.5 ps， 重构信号与原始信号的相似度为 92%。
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