| 摘要 |
Movement of a mouse or joy stick is detected by optically tracking with a navigation sensor the change in position of the micro-texture on a ball instead of using the ball to actuate shaft encoders. The interior of the mouse or joy stick is an optically controlled environment where the external ambient illumination is excluded, the angle, and intensity of a desired illumination is established once, and the only surface to be imaged and tracked is a part of the ball. As the ball rotates a portion of the old image passes from view as a new portion emerges. Consecutive images are represented internally within the optical tracking mechanism as arrays of pixels, and the tracking mechanism tolerates the disappearance of some pixels along one side of the field of view whilst other pixel appear from the other side of the field of view. Pattern matching of unchanged pixels determines movement. The pattern described by the new pixels need not have any relationship whatsoever to that represented by the disappearing pixels. That is, the ball need not have either a known or a precision pattern upon its surface; the surface can have an arbitrary micro-texture. Any wear and tear to the ball, or dirt that gets on it, simply appears as micro-texture to the optical tracking mechanism. Since the micro-texture is expected to be arbitrary anyway, these phenomenon are of little concern, so long as they do not mechanically interfere with the motion of the ball.
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