A new ultrasonic imaging system is proposed which uses a moving asymmetric random phase mask with a δ correlated property. It is shown that the system can achieve higher resolution and less attenuation compared with a conventional system using second‐order correlation‐function analysis. The system presented in this letter also has the advantage that it is not affected by additive Gaussian noises which are independent of the signal. The usefulness of the system is demonstrated by experimental results for one‐dimensional objects.