Lensless “Ghost” Imaging with Thermal Light Sources (abstract)

Correlated two‐photon imaging, also known as "ghost" imaging, has attracted much attention and debate in recent years. The earliest experiments were performed with entangled light, and later with quasi‐thermal light. Our group was the first to use true thermal (incoherent) light to demonstrate two‐photon imaging and interference. We successfully realized lensless ghost imaging with true thermal light at 692.9 nm from the buffer gas in a hollow cathode lamp. The object was a mask with two pinholes separated by 3.66 mm. Furthermore, we analytically studied the effects of higher‐order intensity fluctuation correlations on high‐order ghost imaging and interference, and found that visibility can, in theory, approach the maximum value of 1 as the order increases to infinity. Our experiments on lensless high‐order ghost imaging with a quasithermal light source for orders up to 10 demonstrate that visibility does indeed improve dramatically as the order increases. It is thus possible that high‐order lensless ghost imaging with thermal light may find useful application where conventional imaging techniques are impractical or impossible to use.