Resolution limits for coherent optical imaging: signal-to-noise analysis in the spatial-frequency domain

We investigate the way in which errors arise in photocount-limited, coherent imaging systems and how such errors fundamentally limit the quality of images formed. To reflect the best possible imaging performance with a given optical system, we utilize a continuous-photodetection model to describe the operation of the image-recording mechanism, in which the image-plane camera records the exact x and y positions of each photodetection event produced by the detected coherent field intensity. Using this continuous-detection model and well-known statistical properties of. laser-speckle patterns, we compute the signal-to-noise ratio of the complex Fourier amplitudes estimated by the detected coherent image. With the help of computer-simulated coherent imagery, we illustrate how this expression can be used to characterize the effective resolving power of multiple-snapshot coherent imaging systems.