Touch projection system

A touch projection system, comprising:

• a screen;
• a light source device for emitting projection light;
• an image-capturing device for receiving image light from the screen;
• and
• a micromirror device for reflecting the projection light and the image light, the micromirror device comprising a plurality of micromirrors arranged in an array, the micromirror being controllable to be selectively located at a first angled position, a second angled position, or a third angled position, the micromirror having a first normal direction, a second normal direction, and a third normal direction corresponding to the first angled position, the second angled position, and the third angled position;
• wherein, when the micromirror is located at the first angled position, the projection light from the light source device is reflected by the micromirror and travels in a first reflection direction to be projected onto the screen;
• when the micromirror is located at the second angled position, the image light from the screen travels to the micromirror in a reverse direction reverse to the first reflection direction, is reflected by the micromirror, and travels in a second reflection direction, and the second reflection direction and the first reflection direction are nonparallel;
• and
• when the micromirror is located at the third angled position, the image light from the screen travels to the micromirror in the reverse direction, is reflected by the micromirror, and travels in a third reflection direction to be received by the image-capturing device, and the third reflection direction is nonparallel to the first reflection direction and the second reflection direction.