Abstract: A method for calibrating position of light point is used for an interactive projection system including an image capture device. The image capture device includes an image sensor and an optical filter. The method includes the following steps. A plurality of calibrating patterns formed by visible light is individually projected on a screen. The distance between the calibrating pattern with big area and an optical axis of the image sensor is larger than that between the calibrating pattern with small area and the optical axis. Next, the exposure time of the image sensor is adjusted so the image sensor can capture the images of the calibrating patterns through the optical filter. According to the images of the calibrating patterns, a plurality of coordinate positions is gotten. Then, the coordinate positions are adjusted according to a standard coordinate.

Abstract: A speaker unit for a projector includes a first speaker, a fixing portion and a second speaker. Either the first speaker or the second speaker has a central hole to hold the vertical post of a projector. Two holes that are diagonally opposing each other are provided in the inner wall of the central hole. The two holes of the fixing portion may align with the two holes of the first speaker and fasteners may be used to fixedly connect the first speaker with the vertical post. A connective portion is provided on either of the two vertical walls of the first speaker and a connective portion is provided on either of the two vertical walls of the second speaker. Therefore, the second speaker may be connected with the first speaker by these connective portions.

Abstract: A briefing system is used to project images onto a projection screen to form a projection picture. The briefing system comprises a pointer, a projector and a computer electrically connected to the projector. The computer outputs an image signal to the projector. The projector projects an image corresponding to the image signal onto the projection screen to form the projection picture. The indicator is used to project an indication point. The projector also captures the image of the projection picture and the indication point and transfers the image to the computer. The computer then calculates a location where the cursor on the computer screen should reach according to the location of the indication point on the projection picture and moves the cursor on the screen to there.