LED-based digital holography

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.