Single photons are under study and research because of their application in quantum communication and also in fundamental issues of quantum physics. Considering this fact, imposing changes in the emitted photon is of great importance. In this paper, NV (Nitrogen vacancy) diamond system has been chosen as single photon source and by applying the existing methods for being the related levels in dark state, it has shown that the effect on the emitted photon can be regarded as an improvement for the single photon source. For this aim, second order coherency function is used and it is observed that its value will be decreased.