Method of setting auto focus for mobile projector

PURPOSE: An auto focusing method using a mobile projector is provided to have no need to change a screen into an image of a specific pattern and reduce a session for performing an AF performance because the AF performance is performed by receiving a projection region through a camera unit and detecting an edge value of the received projection region. CONSTITUTION: A mobile projector comprises a projection system(301), a camera part(305), an edge detection logic(307), and a controller(309). The projection system projects a picture output in an output unit on a screen as an image. The camera part receives an edge value of the received input image containing the projected image. The edge detection logic detects an edge value of the received input image. When an auto focusing performance request is received, the controller controls the edge detection logic to detect the edge value of the input image. The controller automatically controls a focus of a mobile projector by using the detected edge value.