LED光源数字全息技术研究

LED-based digital holography

  • 摘要: 研究以发光二极管(LED)作为光源的部分相干光数字全息技术。首先研究LED的时间相干性和空间相干性,尽管LED的时间相干性较差,但空间相干性可以通过减小光源发光面积来提高。利用LED的时间相干性较差、相干长度短的特点,抑制相干噪声,改善数字全息重建质量。在同一全息记录系统,通过实验,比较了用激光和LED光源的数字全息重建图像质量。结果表明:基于LED光源的数字全息,完全消除了使用激光光源的散斑噪声和由光学元件引入的寄生干涉噪声,物光场的重现质量,包括振幅和相位都得到了很大提高。但由于LED光源的较低的空间相干性,一般只适用于同轴相移数字全息,待测物体的厚度在十几微米以内,应用受到一定限制。

     

    Abstract: The short coherence digital holography based on LED was studied. The time coherence and spatial coherence of the LED were studied respectively. Although the time coherence of the LED is very short, the spatial coherent of the LED can be further improved by decreasing the area of the light source. The noise in digital holography could be suppressed by utilizing the short coherence and the quality of the retrieved field is enhanced. The digital holography by means of laser and LED was carried out respectively,then the quality of the reconstructed fields were compared. The results show that the speckle noise and multiple reflections, which are introduced by laser source, are completely eliminated in the digital holography based on LED. Consequently, the quality of the reconstructed object field, including amplitude and phase distribution, is greatly improved. However,owing to the short coherence of LED,the application is confined to in-line digital holography, the thickness of the object to be measured should be no longer than tens of microns.

     

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