A 3D imaging system based on time-of-flight( TOF) principle is designed. This ranging system operates with near-infared light emitted by active modulation light source
which is detected and demoduated by a low-cost CMOS array of pixels based on TOF. ARM and FreeRTOS are used to control the data acquisition module and process raw data. Computer terminal communicate with ARM via universal asynchronous receiver transmitter( UART). The depth information is obtained by using four-step phase-shift algorithm and the 3D point cloud is reconstructed. The test result shows that measurement precision of the system is 1 cm.