Thread: Inside the mouse

The main goal of any mouse is to translate the motion of your hand into signals that computer can use. Among various versions, the opto-mechanical mouse is widely used. It does the translation with the help of five components; ball, two rollers, shafts, infrared LED and sensors, and a chip. The outer shape of the mouse greatly depends upon the manufacturer, but the overall scheme is almost identical.

The mouse ball is a hard rubber ball situated inside the mouse. Touching the ball are two small plastic wheels known as rollers - one placed vertically and another one placed horizontally. Whenever the mouse ball moves, the rollers spin and detect the X (left and right) and Y (top and bottom) movements of the ball. The other side of the roller, there is a small plastic stick known as shaft. And at the end of the shaft is small disk with small holes. Since roller, shaft and disk are all inter-connected, the movement of ball results in disk's rotation.



On the other side of the disk there is an infrared LED and infrared sensor. The holes in the disk break the beam of light coming from the LED so that the infrared sensor sees the pulses of light. The rate of the pulsing is directly related to the speed of the mouse movement and the distance it travels. The chip reads the pulses from the infrared sensors and turns them into binary data that the computer can understand. The chip sends the data to the computer through the cable attached to the mouse.

With the advancement in technology, some mouse does not come with rollers. The task of rollers is replaced by the shafts - which means instead of rollers making contact with the ball, shafts directly touches the ball as well as rotates the disk. Thus mouse movements are translated more quickly, although it is matter of few milliseconds.