The role of narrowband filtering in improving signal-to-noise ratio of   ghost imaging with thermal light background
  In ghost imaging with narrow-band signal in thermal light background, signal arm filters bring higher value and upper limit of signal-to-noise ratio (SNR), and faster speed to reach that limit. The narrower bandwidth, the better. 
Dongyue Yang, Junhui Li, Guohua Wu, Bin Luo, Longfei Yin and Hong Guo
physics.optics