In a structured light system, coded patterns are the key of the corresponding point problem,for their reliabilities directly affect measuring accuracy and resolution. In the paper, an analysis of the maximum stripe deformation (due to depth changes on the surface) and measuring resolution limits are discussed and the principle of spatial periodicity used for coding is proposed. Results show that when spatial periodicity is used for coding, the resolution is greatly improved, or the number of patterns is greatly reduced for real-time structured light systems. According to these analyses, a novel coded pattern based on spatial periodicity for real-time structured light systems is presented as an alternative to the time-space coded pattern. The coded pattern allows range scanning of moving objects with easy implementation for decoding and high measurement resolution. Experiments demonstrate the validity of spatial periodicity used in coded pattern design.