激光显示中散斑减弱的研究

简述了散斑的形成机理,具体分析了在近场条件下通过降低激光的时间或空间相干性来抑制散斑的方法,以及仅通过降低激光的相干性来减弱激光显示中散斑的缺陷。提出一种全新在远场条件下减弱散斑的超声光栅法,且详细说明了超声波减弱散斑的工作原理。当合成的激光束通过因超声波在液体媒介中的传播而形成的"位相光栅"时,激光发生衍射,通过一系列透镜将所有衍射光完全会聚到投影屏幕上,投影移动的干涉条纹在屏幕上产生"沸腾"的散斑图样,考虑到人眼的视觉暂留特性。散斑在人眼中得到均匀化。以绿光为例,说明了激光束通过"位相光栅"时,经过CCD相机和图像处理系统,显示屏幕上散斑对比度和光强的变化,显示了超声光栅法有效地抑制了激光显示中的散斑现象。

Speckle Reduction in Laser Display

This paper summarizes how laser speckle is formed.Many methods of suppressing speckle are de- tailed in the near field by reducing or eliminating temporal or spatial coherence of the laser in the hard core of the thesis,and disadvantages are simplified to reduce speckles only by changing the coherence properties of laser in the far field such as in laser TV.The novel method ultrasonic grating is put for- ward to reduce speckles,furthermore,the operating principle of ultrasonic reducing speckles is illustra- ted in detail.When combined laser beam passes over"phase grating"generated as ultrasonic wave tra- vels in a liquid cell,diffraction occurs.The lens collects the diffracted light and projects it onto the screen.The overlapping beams on the screen produce a moving interference fringe,the movement of these fringes produces a boiling speckle pattern,which gets averaged in the observers'eyes.Finally speckle contrast and light intensity is explained by CCD camera and image processor system,when combined laser beams pass"phase grating"by taking example for green beam,which effectively reduce speckles in laser display owning to"phase grating"generated by traveling ultrasonic waves in the medium.