Study of digital quadrature techniques applied in active laser surveillance

Based on the optical systems' "cat' s eye" effect,a new technique working with single frequency modulated CW laser against IR scanning imaging systems is provided.The retrodirective reflection of the optical systems against the incident laser is discussed and based on the analysis of echo signals' characteristics.A digital quadrature coherent detector is used to detect such signals with low S/N ratio and the expected results is obtained in experiments.