Abstract: An optical touch apparatus and a touch method thereof are provided. A plurality of light sensing units are disposed between a first scanning light source and a second scanning light source, wherein the light sensing units, the first scanning light source and the second scanning light source are disposed at a same side of a touch surface. A touch position of an input tool is determined according to an intensity of a scattered light generated by an input tool and sensed by the light sensing units and generated when a first scanning beam and a second scanning beam scan the input tool.

Abstract: The invention provides a touch module and an operation method thereof. The operation method of touch module includes following steps: detecting a touch point; judging whether the touch point is normal touching according to a detected result of the touch point; when the touch point is abnormal touching, reducing the intensity of an infrared laser of the touch module; and when the touch point is normal touching, judging out the position of the touch point. By using the operation method of touch module, it can reduce or avoid the injury of the infrared laser on the vulnerable portions of human body as abnormal touching.

Abstract: An optical device for controlling a projector is provided. The projector projects a projection image. The optical device includes a receiving module, a mode switching module, and a transmission module. The receiving module is capable of sensing a reflected signal of the projection image. The mode switching module is capable of generating a control signal to control the projector to switch from a first mode to a second mode. The transmission module is capable of transmitting the reflected signal and the control signal to the projector. A projection system including the projector and the optical device is also provided.