The biggest problem faced in the application of optical under-screen fingerprint identification technology is that the finger reflects back more light information, and the information of the fingerprint is interfered by a lot of stray signals, which i s solved by the appearance of ultra-thin under-screen fingerprint identification materials. Using high transmittance core glass and light shielding cladding glass, the preparation process of fiber optic panel is used to obtain the under-screen fingerprint identification material composed of micron-level 2D optical waveguide collimated array. The test results show that the ultra-thin under-screen fingerprint identification material has a good collimation and selection effect on the reflected light signals from the peaks and valleys of the finger, the light shielding glass absorbs the reflected light signals from the large angle, and the high transmittance core glass conducts the collimated and small-angle reflected light signals, so that a clear fingerprint image can be obtained. The development of ultra-thin under-screen fingerprint identification material provides feasible for ultra-thin 5G cell phones.
The waveguide screen, as the core element of the digital CT system, is composed of the microchannel array and the scintillator combination. Using the excellent X-ray absorption performance of high-lead equivalent glass empty tubes and combined with the preparation of microchannel array technology, a glass empty tubes array material with high X-ray absorption performance is prepared.The results show that the high lead equivalent glass empty tubes has good pulling ability, the microporous array size is uniform and controllable, the empty tubes array has high X-ray absorption performance, and has excellent imaging effect after filling the scintillators, which provides a new way for the preparation of the high-performance X-ray waveguide screen.
The existence of blemishes deteriorates the imaging quality of fiber-optic imaging elements and reduces the yield of finished products in factories. The effective detection of blemishes is a prerequisite for analyzing the causes of blemishes and preventing their generation. An independently developed detection device for fiber-optic imaging elements based on machine vision is implemented to detect blemishes automatically and accurately. The blemish distributions of three typical fiber-optic imaging elements, including a fiber-optic plate (FOP), a fiber-optic inverter (FOI), and a fiber-optic taper (FOT), are compared with each other, and the causes of blemishes in fiber-optic imaging elements are analyzed. The distribution of blemishes in the FOP is random, and the average number (AN) of blemishes in the first zone (central zone) and the second zone (outer zone) with the same area is similar. The AN of blemishes for the FOI prepared by twisting the FOP at high-temperature increases from 272.8 (FOP) to 2125.0, and the AN in the outer zone is 1542.5, higher than that in the central zone. More blemishes are generated by the twisting process, and the distribution of these blemishes is close to the outer zone. A significant amount of chicken wires is found in the outer zone, but the majority of blemishes are still spots. The AN of blemishes for the FOT prepared by stretching the FOP increases from 383.0 (FOP) to 515.0, which is attributed to the increase of the number of blemishes in the first zone from 190.8 to 427.0, but the AN of blemishes in the second zone decreases from 192.3 to 88.0. The stretching process stimulates the formation of blemishes with a distribution that is close to the central ring. These blemishes are randomly distributed inside or at the boundary of the multifiber. Most of the blemishes are still spots.
As the core component of image intensifier, the electronic multiplication performance of microchannel plate determines the ability of the device to detect weak signals. The theoretical model of electron gain is the theoretical basis for the secondary electron multiplication of microchannel plates. It has important theoretical significance for the research of high performance microchannel plates and image intensifiers. In this paper, the theoretical model and simulation of electron gain in microchannel plates are reviewed. The electronic gain model and the modified theoretical model of the "energy proportional hypothesis" are emphatically introduced. On the basis of the model, some improvements are made and good simulation results are obtained. The behaviors of electron transport, collision and multiplication in microchannels based on the theoretical model of electronic gain and Monte Carlo stochastic calculation method are summarized. The differences among the three models are analyzed, and the problems existing in the theoretical model and simulation of electronic gain at present are analyzed. Finally, aiming at the shortcomings of theoretical model and simulation, the direction of improvement and optimization is put forward.
The s parameter of the gain theory of microchannel plate directly affects the value of each secondary electron emission coefficient. The electron gain is the accumulation of all secondary electrons, so the s parameter has an important influence on the theoretical value of the electron gain. In this paper, two kinds of clad glass and the same core glass materials are used to fabricate two kinds of microchannel plates under the same process conditions, and measured the electronic gain values. Meanwhile, the theoretical model of the electronic gain of the microchannel plates is established by Monto Carlo stochastic mathematical method, and the s parameters of two kinds of microchannel plates were fitted by the model combined with the measured electronic gain values. On the fitted value of S parameters, the variation of the microchannel plates gain and electron transit time with the microchannel plates applied voltage at both ends, channel bias angle, channel length-to-diameter ratio and output electrode penetration depth is simulated, and compared with the corresponding measured results, the coincidence is high. The relationship between electron gain with bias angle and output electrode depth, and the relationship between Gain with Length/Diameter ratio under different voltage is obtained. Besides, this paper get the relationship between Electron transit time and Full width at half maximum (FWHM) with the different Voltages. The results of this study provide support for the calculation of theoretical electron gain of microchannel plates in different clad glass systems.
Micro-channel plate is an electronic multiplier element with two-dimensional hollow glass tube array structure, which has been widely used in low-light-level night vision imaging, particle detection and other devices. Bulk resistance of microchannel plate is an important performance index, which affects the electronic multiplication performance, dynamic response range and time resolution of micro-channel plate. There are many literatures about the influence of the preparation process of microchannel plate on bulk resistance, but few reports about the influence of the working conditions of microchannel plate on bulk resistance. In this paper, we mainly study the influence of micro-channel plate voltage and ambient temperature on bulk resistance, and analyze the mechanism of the change by tunneling. The results show that: 1) The change of working conditions leads to the change of the bulk resistance of the micro-channel plate. The higher the temperature and the voltage of the micro-channel plate, the lower the bulk resistance of micro-channel plate. The larger the original bulk resistance, the smaller the change rate of the micro-channel plate is. 2) The phenomenon that the resistance of micro-channel plate varies with the use conditions conforms to the mechanism of tunneling conduction.
Optic fiber imaging elements are used in weak visible light, X-ray imaging and high-energy particle detection imaging devices. They play an important role as input and output window materials of image intensifiers. Optic fiber imaging elements are arrays of tens of millions of micron-scale single optical fibers arranged regularly. The fabrication process requires several times of fiber drawing and secondary thermal processing such as hot melting pressure, torsion, and stretching. After these processes, there may be spots and linear chicken filaments that are called defects existed on the interface among the fibers and multi-fibers. Due to these defects, the quality of imaging is seriously reduced, and even the misjudgment or omission of image signal recognition can are caused. How to detect such defects has no an ideal solution. Currently, non-quantitative microscopic observation is generally used. This method, however, is high in misjudgment and low in detection efficiency. In this paper, a device for automatic detection of optical fiber image defects based on machine vision algorithms, including its working principle, structure, detection steps and characteristics are introduced. The device not only can automatically measure the size of each defect, but also can count the defect distribution according to the quality zones. The test results are stable and accurate. It is especially suitable for batch detection and research of optic fiber imaging elements.
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