A new three-dimensional imaging system has been needed to overcome the problems of the prior arts using conventional variable focal length lenses, which have slow response time, small focal length variation, and low focusing efficiency, and require a complex mechanism to control it. The three-dimensional imaging system of the present invention uses the variable focal length micromirror array lens. Since the micromirror array lens has many advantages such as very fast response time, large focal length variation, high optical focusing efficiency, large size aperture, low cost, simple mechanism, and so on, the three-dimensional imaging system can get a real-time three-dimensional image with large depth range and high depth resolution.