共查询到19条相似文献,搜索用时 171 毫秒
1.
2.
3.
4.
5.
6.
7.
8.
基于机器视觉系统OpenMV,以迈克耳孙干涉仪干涉条纹为研究识别对象,根据光源相干性及干涉条纹动态特性,提出基于灰度采样统计的干涉条纹识别检测算法(干涉条纹同心形态搜索算法),运用MicroPython或Python语言编制实时检测程序,运行结果表明仿真和真实干涉条纹都得到了可靠的检测,精度为0.5个条纹,并且测量不确定度主要由算法制定的此条纹检测精度引起,证明了干涉条纹机器视觉检测方法和技术的有效性. 相似文献
9.
10.
用数字滤波消除散斑条纹图噪声 总被引:3,自引:2,他引:1
本文讨论了散斑摄影条纹图的噪声来源及模型,设计合适的数字滤波器.采取正交实验手段,全面分析了噪声、条纹对比度和密度对条纹方向及间距测量精度的影响. 相似文献
11.
Hua Tang Baoqiang Wang Bin Luo Anhong Dang Hong Guo 《Applied physics. B, Lasers and optics》2013,111(1):149-154
The analytical expression for scintillation index of radial Gaussian beam array with coherent combination based on Kolmogorov power-law spectrum in the horizontal path is derived. The influences of the beam number and ring radius on the scintillation index are studied. The results show that the scintillation index can be reduced by increasing beam number and an optimum ring radius is proved to exist. Further, the optimum ring radius greatly depends on the source size and exists only in a certain range of the source size determined by the propagating distance. Additionally, the scintillation index distributions at the receiver greatly depend on the source size. 相似文献
12.
Zernike phase contrast microscopy is extended and combined with a phase-shifting mechanism to perform quantitative phase measurements of microscopic objects. Dozens of discrete point light sources on a ring are constructed for illumination. For each point light source, three different levels of point-like phase steps are designed, which are alternatively located along a ring on a silica plate to perform phase retardation on the undiffracted (dc) component of the object waves. These three levels of the phase steps are respectively selected by rotating the silica plate. Thus, quantitative evaluation of phase specimens can be performed via phase-shifting mechanism. The proposed method has low "halo" and "shade-off" effects, low coherent noise level, and high lateral resolution due to the improved illumination scheme. 相似文献
13.
In recent years researchers in jet turbulence and jet noise have become increasingly interested in what is termed “large scale coherent jet structures”. There is now considerable evidence that azimuthally coherent structures can be generated by acoustically forcing a jet from upstream. However, the evidence for such structures in unforced jets, except close to the nozzle at low Reynolds numbers, is, at best, circumstantial. The role of such structures in subsonic jet noise production is also completely unproven. In an attempt to establish a link between azimuthally coherent structures and the jet noise field a number of experimenters have recently made azimuthal cross-correlation measurements of either the near field pressure or far field noise, and used the observed coherence to infer the existence of an azimuthally coherent source field. The term azimuthally coherent is used here to infer that the source region is dominated by low order azimuthal components, with relatively little contribution coming from the higher azimuthal components. The purpose of this paper is to question the interpretation of that data. Specifically the sound field generated by a simple ring source with various types of azimuthal coherence is considered theoretically. It is shown that the azimuthal coherence of both the near and far field pressures is principally a function of the Helmholtz number and in many cases of practical interest is relatively insensitive to any coherent structure of the source. 相似文献
14.
Based on the partially coherent optical theory, a new theoretical model is established about the X-ray light source radius of X-ray phase contrast imaging system. Through the integral phase contrast modulation transfer function, a comprehensive analysis about the light source radius is made. Then the light source radius selection methods are investigated. Finally, an actual imaging experiment is shown to confirm the choice method of light source radius in X-ray phase contrast imaging system. 相似文献
15.
From the study of the dynamics for the ring-like soliton clusters, we find that there exists a critical value of the ring radius, dcr, for the stationary rotation of the clusters with respect to the beam centre even in the presence of the relatively strong noise, and that the soliton clusters will not rotate but only undergo periodic collisions in the form of simple harmonic oscillator if the ring radius is large enough. We also show that the direction of the rotation can be opposite to the direction of phase gradient when the relative phase difference is within the domain 0 〈 |θ| 〈 π, while along the direction of phase gradient when the relative phase difference is within the domain π 〈|θ| 〈 2π 相似文献
16.
In measuring acoustic field vector properties either complete or partial cancellation between ambient noise energy flux and the oppositely directed one, radiated, for instance, by tone or noise-shaped point source can be found. In that case there is no matter coherent or incoherent fields interact. The phenomenon of interest is named compensation of opposing energy fluxes. The paper is focused on interaction between vertical component of the surface noise energy flux and that of bottom-reflected noise-shaped interfering signal from on-water source in the deep open ocean. Bottom-reflected weak broadband interfering signal measures the extent of resultant compensation. As the vertical projection of the signal energy flux makes the interference maximum, its power appears to be comparable to that of the surface noise and complete compensation takes place at a given frequency. Once it is the interference minimum, just partial compensation can be found. No compensation was observed for co-directional energy fluxes. 相似文献
17.
Laser array beam propagating through mouse liver tissue is investigated. The turbulence power spectrum of the liver tissue is employed in the extended Huygens–Fresnel method to obtain an optical intensity profile and beam broadening at the observation point in biological liver tissue. Variations of the beam profile and the beam broadening are simulated based on the number of beamlets, source size, wavelength and the ring radius of the array. A biological tissue, illuminated by the laser array beam, exhibits different beam profiles and beam spot radius variations when the number of beamlets, source size, wavelength and the ring radius of the laser array beam are varied. Examining these variations observed in the propagated optical beam and comparing them with the test cases, abnormalities such as cancer and tumor in a biological liver tissue can be diagnosed. 相似文献
18.
Gori F 《Optics letters》2005,30(21):2840-2842
A general condition is derived for the distance beyond which the far-zone approximation can be used in studying propagation of light from a partially coherent source. The distance steadily increases as a function of the coherence radius across the source, reaching the usual value in the coherent limit. 相似文献
19.
The effects of two kinds of coherent lengths, the wave packet length of the emitter and the radius of the coherent source, on pion spectrum distribution are studied. It is shown that both coherent lengths can cause abundant pions at low momentum. Observing abundant pions at low momentum may be taken as a signal of DCC effects. 相似文献