Based on the photon Doppler velocimetry technology, this paper studies high-speed targets' three-dimensional (3D) velocimetry technology, reproduces the movement trajectory of high-speed targets through 3D coordinates and broadens the photon Doppler velocimetry technology application scope. First, design the multiplexed photonic Doppler velocimetry optical path structure and analyze the multiplexed photonic Doppler velocimetry principle. Then, the target 3D velocity extraction method is studied, including the fiber optic probe's spatial arrangement and the calculated method of target motion trajectory. Finally, the detection sensitivity of velocity in the direction of the 3D coordinate axis is analyzed. In order to verify the reliability of 3D velocimetry technology, the paper is described in two parts: software simulation and experiment. MATLAB is used to simulate the principle of 3D velocimetry technology. The simulation results show that 3D velocimetry technology can be realized by processing Doppler frequency shift voltage signals. In the experimental part, the high-speed target is detected through fixed-angle optical fiber probes, and four sets of Doppler frequency shift voltage signals are collected. After data processing, the target's 3D velocity is extracted, and the target's motion trajectory is reproduced. Therefore, this paper provides an idea for reproducing the target's motion trajectory by obtaining the high-speed target's 3D velocity.
The infrared anti-reflection film is prepared by ion beam assisted thermal evaporation deposition technology. The film has good firmness and can meet the needs of wet transfer. By adjusting the number of layers of the graphene mesh, the electromagnetic shielding and optical transparency properties are simultaneously improved. The infrared anti-reflection film and graphene mesh are combined to design and prepare a compatible electromagnetic shielding infrared anti-reflection film device with sandwich structure. The test results of the device show that the peak transmittance of the graphene mesh/infrared film/substrate/infrared film combination structure in the 3 to 5 μm band is 95.06%, and the average transmittance is 93.40%. The peak shielding effectiveness (SE) in the 12 to 18 GHz frequency band is 14.50 dB, and the average SE is 12.98 dB. It shows that the film device of this structure maintains the high transmittance of the infrared anti-reflection film and has good electromagnetic shielding effectiveness.
When detecting ultrahigh speed micro targets, because the photon Doppler signal will be seriously interfered with by high-frequency noise, it is difficult to accurately extract the beat frequency information, resulting in serious speed demodulation error. Therefore, we propose a beat frequency extraction method for high-speed and high-noise Doppler signals based on double correction, which can accurately correct the beat frequency signals of high-frequency noise interference. First, the ratio correction method is used for the first spectrum correction to screen out the normalized spectrum of high-frequency noise interference; then, according to the degree of noise interference, the energy barycenter correction method or linear interpolation method is used for the second spectrum correction. Numerical simulation results show that this method can reduce the spectral error by 1.6% to 2.1%. We used this method to process the Doppler signal from the detonation small flyer experiment in Initiating explosive device testing. The results show that it can reduce the beat frequency error by 1.83 times at most under high-frequency noise interfered, equivalent to the instantaneous velocity error of 1955 m/s can be decreased after velocity demodulation. Therefore, the beat frequency extraction method based on double correction has good noise resistance and reliability. We corrected the different regions’ frequency spectrums according to the noise interference intensity, which provides an idea for the beat frequency extraction of high-speed and high-noise Doppler signals.
Schlieren technology can realize the visualization of flow field testing. The transmission schlieren device as a model, a laser light source with Gaussian distribution is used to pass through a cylindrical area with uniform refractive index distribution to obtain a simulated schlieren image and a flow field visualized diffraction fringe. Based on the theory of Fourier optics and applying Fresnel diffraction optics technology, the Fourier characteristics of the lens are derived, and the light field distribution at the focal plane of the lens is calculated. The Heaviside step function is combined to express the light field distribution on the back surface of the knife-edge device, and then the light field intensity expression of the imaging plane is obtained. The results show that the transmission schlieren method can obtain a high imaging quality light field intensity distribution map containing the parameters of the test object. When the cutting position of the knife edge is half of the light field spectrum surface, the imaging plane display effect is the best. In the comparative experiment, when the knife-edge device cuts the spectrum surface 2/5~1/2, the test object parameter information contained in the light field intensity map is the most complete. The intensity of the part that is shielded by the knife edge device is 0, and the intensity of the unshielded part is constant, which is consistent with the performance result of ray optics. This algorithm can provide theoretical basis and experimental reference for the visualization of typical flow field.
As the supporting experimental platform of the Xi'an Technological University education reform experimental class, “optical technological innovation experimental platform” integrated the design and comprehensive experiments of the optical multi-class courses. On the basis of summing up the past two years teaching experience, platform pilot projects were improve. It has played a good role by making the use of an open teaching model in the cultivating engineering innovation spirit and scientific thinking of the students.
With the increasing number of the graduate students, many of them have some troubles in job finding. This situation make a huge pressure on the senior students and loss them the interesting in study. This work investigate the reasons by questionnaire survey, panel discussion, interview, etc. to achieve the factors influence their learning interesting. The main reason of students do not have the motivation on study is that they do not understand the development and competition of photoelectric specialty, lack of innovation and entrepreneurship training, hysteresis of the learning knowledge and practical application. Finally, the paper gives some suggestions through teaching reform on how to improve students' learning enthusiasm. This work will contribute to the teaching and training of senior undergraduate students of optoelectronics specialty.
Diamond-like carbon (DLC) films have attracted much attention because of their excellent performance; however, the low anti-laser damage ability of such films seriously restricts their applicability. To overcome this problem, applying the bias field to the DLC film could slow down the DLC film graphitization process and improve the LIDT of the DLC film. Results showed that the longitudinal electric field could decrease the sp3 hybridization to sp2 hybridization, prevent the formation of sp2 clusters. in this study, Unbalanced magnetron sputtering (UBMS) was used to deposit a diamond-like carbon (DLC) film on Si substrates. The refractive index and extinction coefficient of the DLC films were measured using elliptical polarization spectrometer. The transmittance and the surface roughness of DLC films were examined using optical microscopy, SEM, AFM and Raman spectroscopy. Ti electrodes were deposited on DLC films directly, forming a transverse and longitudinal bias field on films’ surfaces. The 3D electrodes morphology of the DLC film was observed. The electrode thickness was measured by a white-light interferometer, and the average thickness of the electrodes was 325.90 nm. The surface roughness of the electrodes was tested using the Talysurf CCI 2000 noncontact surface-measuring instrument, and the average roughness of the electrodes was 0.50 nm. The electrodes have good Ohmic contact and little thermal stress, and it can be used to form a parallel electric field.
Diamond-like carbon (DLC) filmare widely used in the infrared protection window, but their ability of anti-laser damage is insufficient. The common methods to improve the anti-laser ability of DLC films were summarized at first, then a new method which use the external electric field was proposed. Based on the standards ISO11254 of laser damage threshold, the damage morphology of DLC films with and without the bias field were compared. The results show that with the bias field, damage morphologies changes obviously under the same laser energy. According to the physical mechanism analysis, the photogenerated electrons of the films under the action of electric field drift speedy, the drift reduce the heat generated from the laser radiation area, then relayed the graphitization of the DLC films. This after-treated method will be a new method to improve DLC films’ anti-laser damage ability.
In the full-color, high contrast, more accurate color rendition technology, High-Definition (HD) color display requires to
increase the transmissivity of red green blue (RGB) light of ordinary white light and cut-off others in depth. The
ordinarily used discrete tricolor light filter has shortcomings such as energy lose and polarization aberration. In this paper,
a new tricolor light filter was designed and prepared based on thin film technology. The center wavelengths of the
tricolor light filter were determined to be λR=700.0nm, λG=546.1nm and λB=435.8nm, the results showed that the
transmissivity of the filter is less than 7% in cut-off region, and the average transmissivity is greater than 91% in pass
band region. The tricolor light filter can simplify the preparation process, save the coats and increase the transmission
property.
Diamond-like carbon (DLC) films were deposited by the Unbalanced Magnetron Sputtering(UBMS) technique which
was under the conditions of bias 80V, target current 110A, argon flow 200SCCM, excitation current 100A; experimental
platform was built for Laser-induced damage threshold(LIDT). The DLC films was irradiated by the laser (Wavelength
1046nm, pulse width 10ns, laser energy from 0.75mJ/cm2-2.60J/cm2), we got the LIDT of the DLC films is 1J/cm2. The
whole physical process from slight burning, spalling, crack splashing until the substance damage of the DLC films was
observed by 1000 times magnification and interference microscope. Thermal stress is one of main factors that laser
injures films.
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