User:Rtarat

mouse EARLY DEVELOPMENTS:

Early developments: Initially,the mouse consisted of a trackball to navigate.The trackball was invented by Kenyon Taylor,Tom Cranston and Fred Longstaff. Independently, Douglas Engelbart from Stanford university also invented the first prototype in 1963. But te first mouse was not ergonomic as it employed two gear wheels to facilitate movements in the X-Y directions,so, the popular model which is still in use was actually invented by german research facility Telefunken. THis used the popularly known trackball for movement.This would roll in any direction thus enabling free movement.

STRUCTURE AND WORKING

The trackball mouse had two freely rotating rollers that were mounted 90 degree apart.One of the rollers detected the forward-backward motion(movement in Y axis) while the other detected movement in left-right(along X axis).In addition to these two rollers,there was a third roller opposite to the two rollers and mounted at 45 degrees.This was used as a spring to push the trackball firmly against the two motion detecting normal rollers. Each roller is mounted on the same shaft as encoder wheels with slotted edges. These slots intercept infra-red waves to produce electrical pulses that depict the trackball motion. To determine the direction of movement of the wheel,simple logic circuits are used.This is also called Quadrature encoding scheme. The trackball is either made up of steel or hard rubber so as to make it slightly heavy as the weight of the trackball itself helps in navigation.The movement of the trackball correspond to two counts of the cursor,one for the X axis and one for the Y axis. The mouse also contains one left mouse button,one right mouser button and a middle button for the purpose of scrolling up or down a page.The click of the buttons are fed to a microcontroller that send the information to the processor in 3 byte packets via a serial link.

OPTICAL MOUSE

The traditional trackball mouse is now overrun by the optical mouse .It is also called the intelli mouse.It has a digital camera mounted that is used to take pictures,at the rate of almost 1500 per second and the onboard chip determines the direction of movement. It uses a LED(Light emitting diode) that emits light thais bounced from the surface and is detected by a CMOS sensor.The inbuits digital camera captures the image and sends it to a digital signal processor for analysis.The processor analyses the image and compares it with previous images to determine the change in position.This information is then sent to the processor and the corresponding coordinates are then displayed by the cursor.