共查询到20条相似文献,搜索用时 203 毫秒
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根据散斑产生的机理,利用像素点之间干涉的概念,提出了通过限制光场的位相分布范围来抑制投影图像中散斑对比度的方法.在部分发展散斑的条件下,推导了位相均匀分布情况下的散斑对比度公式,揭示了当相位分布范围在0.6π~2π之间时,散斑对比度随相位分布范围的变化而震荡变化,当把相位分布范围限制在0.6π以下时,散斑对比度会随相位分布范围的减小而迅速下降.建立了理想仿真模型和实际仿真模型来验证该方法的正确性和可行性.在理想仿真模型中,当位相分布范围从2π变到0,所得散斑图样对比度从66.44%降到0;在实际仿真模型中,模拟了实际激光投影系统的光路结构,并运用了两片衍射光学元件,一片用于激光整形匀化,一片用于光场的位相分布范围限制,散斑图样对比度从92.78%降低到2.09%.该方法稳定性高、耗能低、使用元件尺寸小,为全息投影显示的散斑抑制提供了参考. 相似文献
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分析了微型激光投影引擎的两种主要光学噪音|干涉网格和激光散斑产生的基理|提出采用振动的随机位相板同时实现干涉网格和激光散斑抑制的方法并进行了理论分析|自行设计了微型激光投影引擎,利用微型电控马达带动随机位相板振动,用CCD相机在不同的F#及曝光时间下对投影图像进行了采集,并对图像的散斑对比度行了测试.结果表明,通过静止的随机位相板可以很好地抑制干涉网格噪音|通过使随机位相板以大于视觉暂留效应形成的融合频率进行振动,可以同时抑制干涉网格和激光散斑,使得散斑对比度小于5%,达到投影观察的要求. 相似文献
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半导体激光器的自混合散斑干涉测量流体速度 总被引:10,自引:4,他引:6
提出了一种简便的激光自混合散斑干涉测量流体速度的方法。根据散斑和法布里-珀罗腔的理论,提出了半导体激光器的自混合散斑干涉模型。研究了流体运动时在半导体激光器内产生的自混合散斑干涉效应(SMPI),给出了激光器输出增益的变化及其概率密度分布。得到了激光自混合散斑干涉平均频率与流体速度之间的关系。模拟计算和实验结果验证了这个关系。利用散斑干涉的平均频率与流体速度的关系测量了高分子材料溶液的速度,并在溶液浓度和背景光变化时,对流体速度进行了测量、比较和分析。实验表明。在溶液浓度不太低时,测量误差小于8%。 相似文献
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计算了圆形、矩形激光光斑对于激光扫描显示系统中散斑对比度的影响.对于圆形光斑,当光斑尺寸大于散射表面相关长度时,得到的散斑对比度随着光斑尺寸变小而下降;当光斑尺寸接近表面相关长度大小时,由于光斑中包含的散射颗粒变少,得到的是非高斯散斑,散斑的对比度反而会变大;随着激光斑进一步变小,由于镜面反射效果散斑的对比度会很快下降.对圆形光斑部分结果给出了实验验证.为了保证光斑中有足够的散射颗粒,只在一个方向压窄光斑,分别计算了平行于扫描方向和垂直于扫描方向压窄光斑得到的散斑对比度.平行于扫描方向压窄光斑,散斑的时间相关性会下降,平均效果变明显,散斑的对比度变小;垂直于扫描方向压窄,散斑对比度变化不大. 相似文献
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半导体激光器内自混合散斑干涉 总被引:1,自引:1,他引:0
在散斑和半导体激光器的自混合干涉理论的基础上,提出了基于法布里一珀罗腔的自混合散斑干涉模型,对粗糙表面产生的激光器内自混合散斑干涉效应(SMSI)进行了详细的理论研究和分析,得到了粗糙腔条件下的激光动力学的数值解。模拟产生了高斯相关随机表面及其在夫琅禾费面上产生的散斑场,以及该散斑场与相干光场叠加所形成的光场,分析了这些情况中光强的统计特征,与已知实验情况进行了对比,模拟结果与已知统计结果相同。给出了粗糙表面运动时激光器输出增益的变化及其概率密度分布。对由于照明宽度和外腔长度的变化而给粗糙表面运动时激光器输出增益变化带来的影响进行了分析。实验结果和模拟结果相符。 相似文献
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为了精确描述超声散斑场的特性,提出了采用计算机模拟产生超声散斑场的方法.利用模拟产生的高斯相关随机表面,获得了这类表面远场超声散斑场,同时得到了声强分布和相位分布.与实验产生的散斑场进行对比,建立了超声散斑场接收的实验系统,取与计算模拟相同的参数,获得了实验散斑场.通过对比发现:计算机模拟产生的超声散斑场相位存在奇异点,奇异点周围相位分布类似漩涡,计算机模拟产生的散斑场与实验得到的散斑场强度分布相似,强度值比实验产生的散斑场强度大,携带有用信息的高亮散斑较多,暗点较少,更利于研究和分析. 相似文献
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The statistical analysis of self-mixing speckles interference using Fabry-Perot cavity is described based on the theory of the speckle and the self-mixing interference in a laser diode. Speckle signal processing based on Fourier transform is presented in this paper. The linear dependence between the spectrum mean frequency and velocity of solution is given by simulation and proved by experiment. The experimental results show that this speckle signal processing can be used to measure velocity of target. 相似文献
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用偏振和有规位相分布抑制线聚焦系统的小尺度不均匀性 总被引:2,自引:0,他引:2
研究了一种用以抑制光楔列线聚焦系统在靶面产生的干涉尖端的方法。由这种尖峰引起的小尺度不均匀性对X射线激光的产生是不利的。利用特殊分布的偏振态和位相,可把尖峰引向更密度伯程度,而且其对比度下降,这将有利于它通过靶物质自身的横向热传导而平滑化。对于四单元的列阵系统,甚至可将尖峰完全消除。 相似文献
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Chien-Yue Chen Wei-Chia Su Ching-Huang Lin Ming-De Ke Qing-Long Deng Kuan-Yao Chiu 《Optical Review》2012,19(6):440-443
A head up display (HUD) with laser backlight unit has two principle problems; one is laser speckles and the other is distortion. In this study, we propose that a rotating diffuser set at the intermediate image plane of the HUD projection system can simultaneously solve these problems. The conditions of speckle reduction and de-distortion are also estimated in this paper. 相似文献
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We describe in this paper a speckle interferometer constituted by two partially diffusing plates. They are illuminated by a laser and the resulting intensity distribution is observed in the image plane of the source. Each speckle of this plane (Fourier plane) is modulated by a ring system whose interference order depends on its phase. Since the observation plane is a Fourier plane, a longitudinal or lateral shift of one of the diffusers results only into a change of the modulating fringes, the speckles themselves remaining unchanged. A photographic plate which records successively the intensity distribution lying in the Fourier plane before and after the considered shift, exhibits after processing a system of Moiré fringes, the shape of which depends on the nature of the translation given to the diffuser between the exposures. 相似文献
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Hideki Funamizu 《Optics Communications》2008,281(4):543-549
It is known that speckle patterns with fractal properties, called fractal speckles, are produced by illuminating a diffuser with the coherent light having the intensity distribution obeying a negative power law. One of key properties of fractal speckles is the spatial correlation function obeying a negative power law, which implies that such speckles have scaling properties. In detecting fractal speckles, the effect of the spatial integration is inevitable in most cases since they have speckle grains of various scales including very fine ones. To evaluate this effect, in this paper, the contrast of spatially integrated intensity distributions is investigated theoretically and experimentally for fractal speckles. The results show that the contrast reduction with the size of the detector aperture obeys a negative power function related with the exponent of the intensity correlation coefficient of fractal speckles. 相似文献
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Asundi A 《Optics letters》2000,25(4):218-220
Speckles usually are of two kinds: laser speckle and white-light speckle. An additional kind, termed a sampled speckle, is proposed. Whereas laser speckles arise from multiple interference of light scattered from an object illuminated by a coherent laser beam and white-light speckles are a physically generated speckle pattern on the surface of the object, sampled speckles are generated as a result of the sampling of a digital image. The generation of these speckles and their application to displacement measurement are demonstrated. 相似文献
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Yung-Neng Hsiao Hau-Ping Wu Cheng-Huan Chen Yu-Chung Lin Min-Kai Lee Sung-Ho Liu 《Optical Review》2014,21(5):715-718
A laser beam shaping architecture based on a microlens array homogenizer has been exploited, in which the interference effect due to the coherency of the laser source deteriorates the uniformity. Moving diffusers have been considered as an effective way of averaging out the interference pattern. Because the uniformity is required in the line direction only, a one-dimensional reflective-type diffuser with a well-controlled diffusion angle has been proposed and prototyped. The diffuser is attached onto a rotating cylinder for movement in operation. The experiment demonstrates the effectiveness of the scheme, and a line beam with a uniformity of up to 92% has been achieved. 相似文献
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The goal of this paper is to determine hidden periodicities (spatial frequencies) into speckles patterns obtained in a diffuser after reflection of an unexpanded laser beam over an aluminum membrane by means of the so-called Wigner Distribution Function (WDF). These spatial frequencies are used to find the temporal frequencies at which the mechanic system is vibrating. 相似文献
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Junichi Kinoshita Hitoshi Aizawa Akira Takamori Kazuhisa Yamamoto Hiroshi Murata Koji Tojo 《Optical Review》2016,23(1):121-132
Angular dependence of speckle contrast of speckle pattern projected out of a multi-mode fiber connected to a high-power blue laser module is investigated. The laser module has nine high-power InGaN/GaN blue laser diodes arranged in a three-by-three array. Each of the arrayed laser diodes have slightly different incident angle to the fiber. We have successfully extracted the fine screen speckle pattern from the projected pattern mixed up with the coarse fiber speckle pattern by processing the measured data. It is found that the speckle contrast of the both screen and fiber speckles are larger around the center area where the guided-light component closest to the paraxial direction is projected. This is because the output of the center laser in the array is likely to couple into the paraxial mode more than the rest. Speckle contrast behaviors when applying the speckle reduction methods, fiber vibration, diffuser, and spinning diffuser are also investigated. 相似文献