The Research On The Quality Of Ghost Imaging In A Two-color Lens-less Ghost Imaging System

Correlated imaging(also known as ghost imaging),which is a new imaging technique originating from quantum theory,has been discussed widely in recent years.It is a kind of nonlocal imaging technology.The source is split into two correlated beams by a beam splitter,and they travel through two different arms.One of them is called as the test arm which contains an unknown object and a bucket detector,the other is the reference arm which has a high resolution detector.By correlating the intensity fluctuations detected by the two detectors,the unknown object can be retrieved on the detector in reference arm.The first ghost imaging experiment is based on quantum entangled photon pairs from spontaneous parametric down conversion.So,many researchers think that only quantum entangled sources can be used to realize ghost imaging.It is now widely accepted that both classical thermal sources and quantum entangled sources can be used for ghost imaging.The two-color ghost imaging,whose wavelength in the test arm and the reference arm are quite different,was first proposed in 2009.That provides a more extensive resource for ghost imaging.In this thesis,the influence of the wavelength difference on a two-color lens-less ghost imaging system,ghost imaging and ghost diffraction in the two-color ghost imaging system are discussed in detail.The main results are listed as follows:1.The influence of the wavelength difference on a two-color lens-less ghost imaging system is discussed.A very simple expression of the point-spread function is derived,which determines the imaging quality.By the analytical results and numerical simulation,it is shown that the existence of the wavelength difference results in the decrease of imaging quality,and the effect from the wavelength of the object arm on imaging quality is greatly higher than that from the reference wavelength.2.A scheme to recover the blurred image which originates from the wavelength difference is proposed.The theoretical analysis and the numerical simulations show that the imaging quality can be recovered when a glass rod is inserted into the lens-less ghost imaging system.In addition,an expression about the relationship between the length of the glass rod and the wavelength is derived.3.Ghost diffraction and ghost imaging in a two-color ghost imaging system are investigated in detail.It is demonstrated that ghost-image and ghost diffraction(GD)fringes can be obtained by only changing one of the wavelength of two-color source when compared with the result in single-color imaging.The condition of GI and GD in two-color ghost imaging is obtained.It is shown that the conditions of GI and GD in signal-color ghost imaging are a special case of two-color ghost imaging.