A new adaptive contrast enhancement algorithm for infrared images is presented based on histogram equalization.By analyzing the histogram of infrared image,a weight function is gotten adaptively by which the original image’s histogram is weighed.Then,conventional histogram equalization is performed on the original image based on the weighed histogram.With the proposed method,threshold is not needed.Moreover,disadvantages that histogram equalization enhances background are overcome.The proposed algorithm is used to enhance the contrast of infrared images generated from an infrared focal plane array system.Results illustrate that contrasts of processed image are improved significantly.Theoretical analysis and experimental results also show that it is an effective enhancement algorithm for most infrared images.