The advanced multi scale Retinex (AMSR) algorithm was put forward: after enhanced by multi scale Retinex the image of the truncate interval that it was a range near the mean brightness μ in k multiple standard deviation σ had been elected and stretched. According to the ideas of D. J. Jobson et al. if the production of the brightness multiply with the contrast degree for the stretched image was in the range of [6 000, 10 000], the stretched image has high quality. As the same time, the experiments proved the conclusion: the highest quality image in enhanced images for an underexposure color image was that it selected about k=1 multiple standard deviation range near the mean brightness and stretched after enhanced by multi scale Retinex algorithm.
We study the optical bistable properties in one-dimensional photonic crystal with symmetric structure (AB)N(D)M(BA)N, where A is high refractive index medium, B is low refractive index medium, D is defect layer, N is the number of layer periods at the left and right of the defect layer. M determines the thickness of the defect layer with Kerr medium. First, we analyze mechanisms producing bistability by the structure consisted of a nonlinear layer sandwiched between Bragg reflectors. Then by using the transfer matrix method, we calculate numerically the threshold value of the bistability switching in one-dimensional photonic crystals with structure (AB)N(D)M(BA)N. The investigations show that the number of layer periods (N) and the thickness of the defect layer (M) influence the threshold value of the bistability switching. We confirm the parameter of the bistability switching to produce the lower threshold value.