The Optical Mouse - A Replacement for Its Wheeled Counterpart

Physics is the body of knowledge that deals with the understanding of nature and is concerned with the universe's fundamental laws. Optics, in the meantime, is the branch of physics that studies about the properties of light and its behavior and how light interacts with matter.

The advancement in optics has led to the development of numerous optical devices such as the telescope, microscope, correctional lenses, prism, and even CD and DVD readers. One specific optical device that came from the advancement of optics is the optical mouse.

Previously, a computer mouse is of the wheeled model where there is a wheel or a ball at the center of the mouse which when moved, the wheel or ball also turns the parts inside the mouse that will move the cursor to a new coordinate at your desktop. This wheeled mouse model however, is slowly being replaced by a better mouse model that uses optics as the basis of its function.

The optical mouse is now the preferred device for pointing and clicking cursors for computers. This is better than the wheeled mouse model because the optical mouse does not need to have a mouse pad and can be used on any surface that could reflect light. In practice, an optical mouse does not need cleaning, because it has no moving parts. This all-electronic feature also eliminates mechanical fatigue and failure. If the device is used with the proper surface, sensing is more precise than is possible with any pointing device using the old electromechanical design. This is an asset in graphics applications, and it makes computer operation easier in general.

An optical mouse is composed of a light-emitting diode (LED), an optical sensor, and a digital signal processor. The physics behind the optical mouse is that the light-emitting diode (LED) is flashed on the mousing surface and this light is allowed to be reflected for over 1,000 times per second. The optical sensor then takes microscopic snapshots of the mousing surface also at a rate of more than 1000 images per second. The light that is being emitted by the LED is emitted vertically on the working surface; this means that because the light is perpendicular to the surface then the reflection is also perpendicular. The reflection of light therefore would not have an angle of incidence and an angle of reflection. When the optical mouse is move, there is a change in how the light is reflected and would therefore cause changes in the reflection of the light. Movement is detected by the optical sensor and the digital signal processor because of the slightest changes in how the light is reflected on the surface.

When the optical mouse is moved, the surface in which the light is reflected on also changes, these changes produces a different image that the sensor and the DSP would process to generate a usable movement data. These movement data is then processed. Based on the changed patterns over a sequence of images, the DSP will process information and determines how far the mouse has moved and will send the corresponding coordinates to the computer. The computer will then process the corresponding movement of the cursor on the desktop screen. This process is repeated more than a thousand times each second which makes the movement and coordination of mouse and cursor to become very smooth.

REFERENCES:
Hecht, Eugene. 2001. Optics, 4th ed. Pearson Education. ISBN 0-8053-8566-5
"How do optical mice work?". May 08, 2001 http://computer.howstuffworks.com/question631.htm