PURPOSE: An optical device for a touch screen is provided to generate a specific command by using a spindle motor and laser when inputting various data by touching with a pen or a finger. CONSTITUTION: A collimator(230) narrows light of a light source(210) to be parallel light. A polarizing prism(240) changes the direction of the light. An inclined mirror(250) reflects the light again. A detector(270) detects the reflected light. A spindle motor(225) is rotated to emit the light along a surface of a touch screen(A). A synchronization detector(260) detects the rotation synchronization of the spindle motor. An angle of the light emitted to the polarizing prism is 5-20°, inclusive. [Reference numerals] (AA) Light transmission laser; (BB) Light reception laser
