Apparatus for detecting coordinates, display device, security device and electronic blackboard including the same

PURPOSE: An apparatus for detecting coordinates, a display device including the apparatus, a security device including the apparatus, and an electric blackboard including the apparatus are provided to reduce spaces and times required for installing the apparatus. CONSTITUTION: A voltage generating part(11) applies a pre-set driving voltage. A sound wave-voltage converting part(12) vibrates based on the driving voltage from the voltage generating part. The sound wave-voltage converting part generates ultrasound waves. The sound wave-voltage converting part converts the ultrasound waves into corresponding voltage levels by receiving ultrasound waves reflected from a region of interest. A commutating part(13) commutates ultrasound wave reflected positions according to the converted voltage levels.