An in-line phase x-ray imaging prototype was developed based on an innovative dual-detector configuration. In this communication, the design considerations of the dual-detector concept, particularly on the detectors were discussed. Experimentally and with the prototype, signal and noise characteristics were measured. Both attenuation and phase contrast images of selected phantom were acquired. These images offer adequate image quality to facilitate the retrieval of quantitative phase maps of the phantoms. The results demonstrated that x-ray phase imaging is technically feasible under a single exposure; it has potential for improving the accuracy of clinical diagnosis, at reasonable radiation dose.