An idea is proposed to convert optical information of the near field into propagation waves by an isosceles triangle phase-grating coated metal film for super-resolution imaging. We analyzed the reverse process of exciting surface plasmon polaritons (SPPs) by attenuated total reflection coupling mode, and found it was possible and effective to transfer the nanoscale information from near field to far field by the special phase grating. In this article, the excitation mechanisms of the SPPs and the details of the high-efficiency coupling output of the near-field light waves were explored. A special coupling microstructure was designed so that the near-field information could be collected in the far field. We also built an optical transfer function of the superlens imaging system, and reconstructed the simulation image of nanoscale object. Analysis and calculation shows that the isosceles triangle phase-grating coated metal film plays an important role in far-field imaging beyond the diffraction limit, namely, converting evanescent waves to propagating waves and changing the direction of the optical wave by the phase modulation. The methods provide a way to quickly get the near-field information without complicated requirements. (C) 2007 American Institute of Physics.