A Novel Design of Motion Detector Using Mouse Sensor

Mouse Cmos Sensor

The heart of an optical mouse is a mini camera in low-resolution. Just as Figure 1 showed that the navigation LED in the mouse illuminates a surface, and the light reflects off the surface to the lens. When the mouse is moved, the mini camera of the mouse (the sensor) takes continuous snapshots of the surface. The built-in digital signal processor (DSP) would process the data and determine the distance and direction of the movement. Then the micro-controller will send the result to the PC via the USB wire or other communication channel.

Figure 1.

Mouse structure

Figure 2 displays the algorithm of motion detection in the mouse DSP. When the mouse is moved, image A and B are captured by the CMOS sensor continuously. Ref is the same sub-image on both A and B, so that it can be a reference of image for A and B. In other words, it must be made sure that there is something on the image which is captured by the CMOS sensor. Then the DSP will figure out the vector of the movement based on the reference.

Figure 2.

Sketch map for motion detection algorithm

Because the resolution of CMOS of mouse senor is very low (about 200 pixel in our prototype), and the DSP is making use of the algorithm for simple figure and point, the cost of the processor is low. So this is the reason of low power and high speed.