1. Field of the Invention
The present invention relates to the technical field of spot click-event detection and, more particularly, to a multi-trail spot click-event detection method.
2. Description of Related Art
A projector is generally used in conferences or 3D games for casting the content of a computer screen on a curtain, to offer multiple users concurrently to view and discuss topics or play interactive games. However, such a way has many inherent difficulties. For example, for a conference report, a speechmaker uses a laser pen for directing the conference report and a computer mouser for, e.g., changing pages, browsing contents and/or selecting files. This makes the speechmaker appear bustle. In addition, if an operator for changing pages, browsing contents and/or selecting files is added, a mismatch may occur between the speechmaker and the operator. For example, the operator changes a new page because of misunderstanding of the speechmaker's gestures. Further, a substitute for the operator or a user may need to exchange the seats and/or update computer files (such as in an interactive game or an on-line discussion), which is very inconvenient.
To overcome the aforementioned problem, an image capture device (such as PC-camera) is added in the system to monitor a projection screen such that the laser pen can directly be operated on the projection screen. Moreover, detecting and decoding the laser spot's motions in combination with an image analysis and interactive control software can replace the mouse operations. Such a laser pen can overcome the problem to achieve multi-interaction environment. Attendants can use their laser pens for remotely controlling system operation on the projection screen.
U.S. Pat. No. 6,275,214 granted to Hansen for a “Computer presentation system and method with optical tracking of wireless pointer” discloses spot detection steps including: (1) subtraction of a current image and a previous image; (2) comparison of a result (image) after the subtraction and predetermined spot's properties (brightness, color and shape) for filtering different pixels and remaining similar ones; (3) searching the optimal one from the remainders (i.e., possible spots) as a target laser spot; and (4) confirmation a click action when the target laser spot is detected in a small area several consecutive times. However, the system can detect moving spot only. A spot positioned on a fixed small area may not be detected. The predetermined spot's properties can greatly limit the comparison. For example, when the system environment such as projection curtain's size and background light changes, a spot may not be detected or a noise may be detected as a spot.
U.S. Pat. No. 6,346,933 granted to Lin for an “Interactive display presentation system” also discloses a spot detection method, which is similar to the U.S. Pat. No. 6,275,214 except that it applies “brightness” of a spot to the subtraction step and the filtering step. Next, a trail of consecutive spot positions is recorded and analyzed to determine if one of predefined “gestures” is met, and if yes, a related control command is generated. However, the accuracy of such a system may not be reliable due to unstable spot detection. This is because unstable consecutive spot positions may form an undefined gesture, resulting in failure of gesture analysis and generation of error control command. In this case, a “learning” step for the predefined gestures is required, and a new user needs to learn the system again. Accordingly, the system complexity in use is significantly increased.
U.S. Pat. No. 5,115,230 granted to Smoot for a “Light-pen system for projected images” discloses a semi-transparent projection screen laterally located by a projector and an imaging device in front of which a filter is added such that only red laser light can pass through the filter. Therefore, such a spot detection is very simple, i.e., only the “brightness” of spots is applied to image subtraction and threshold filtering. However, due to the semi-transparent projection screen, such a system is very expensive and special so that implementation cost for such a system cannot be reduced.