Unbalanced lensless ghost imaging with thermal light.

Lensless ghost imaging (LGI) with thermal light requires an equal length between the test and reference arms. When this condition is not met, the image becomes blurred. Here we propose an experimental scheme of LGI where the lengths of the two arms are not equal. Our experiment shows that when a glass rod is inserted into a longer arm, the clear image can be formed in the intensity correlation measurement of the two arms. The theoretical analysis can well explain the experimental results. The unbalanced LGI may provide an alternative scheme in practical application.