How does the mouse work?

The computer mouse was invented by Douglas Engelbart and was originally known as the X-Y Position Indicator. This device is better known nowadays as the (computer) mouse, after someone observed that the wire hanging off the device looked like the tail of a mouse. In this post I will be explaining briefly about how a mouse works.

There are two kinds of mice:

• Ball-style mice, and
• Optical mice

The ball-style mice aren't commonly found today, thanks to the newer optical mice.

Ball-style Mice

As the name suggests, the ball-style mouse has a ball that is in contact with the exterior surface and rotates as you move the mouse. The ball then turns an X-axis wheel and a Y-axis wheel which have another wheel with spokes attached to them (somewhat like a cycle wheel). These spokes in the wheel repeatedly break a beam of light as the X and Y axes wheels rotate. A chip in the mouse then counts the number of times this beam of light is broken and moves the cursor by a corresponding amount.

But a question you may have is, how will the mouse determine the direction you move it in, as moving to the right or left would make no difference in the way the beam of light is broken?

Well, there are a pair of spokes that break two beams of light in an alternating manner. By reading this pattern, the chip can figure out the direction of movement.

Fig. 1 A ball-style mouse

This type of mouse, however, requires the use of a special mouse mat and the ball accumulates dust over time negatively affecting its performance. A better thing to do would be to get yourself an optical mouse.

Optical Mice

Unlike the ball-style mouse, Optical Mice use a completely different technology. The way it works is that an LED shines light onto the surface which bounces back into a sensor (photocell) that reports to a chip which figures out your movement by comparing the changing patterns of light and sends it off to the computer. If you look closely at the place where light bounces back into the mouse, you can observe that a lens is placed in the path of the reflected light. This sensor magnifies the light, enabling the sensor to detect your movements with increased accuracy. Have a look at the image below:

  Fig. 2 An Optical Mouse

The use of a special mouse mat isn't necessary, although having one can greatly improve the performance of your mouse. These also don't require much maintenance. These are two reasons that gave the optical mice an edge over the ball-style ones.

Before I conclude the post, I would like to add a few things about how the scroll wheel works. Now, there are many ways in which this can be done. Many mice use potentiometers (or variable resistors, say like knobs on a radio that can turn forever), optical methods (like in the ball-style mouse, remember?) and various other kinds of switches that rotate.

Fig. 3 Notice the spokes in the scroll wheel. This scroll wheel utilises optical technology.

With that, I would like to conclude this post and I hope you liked it. Follow the blog for more such content.

Regards,

Lightspeed

References 

(1) https://www.explainthatstuff.com/computermouse.html

(2) https://en.m.wikipedia.org/wiki/Computer_mouse

(3) https://upload.wikimedia.org/wikipedia/commons/e/e0/Logitechms48.jpg

(4) https://upload.wikimedia.org/wikipedia/commons/thumb/0/0d/%D0%9C%D1%8B%D1%88%D1%8C_2.jpg/1920px-%D0%9C%D1%8B%D1%88%D1%8C_2.jpg (Thumbnail)