You probably noticed this behavior behind an optical mouse: if you do not move it for a long time, the brightness of the LED drops, and if you leave it alone for a few minutes, it starts blinking at all. Is this a malfunction, or is it the way it should be?
To understand why the mouse LED starts blinking, and why it is needed at all, you must first familiarize yourself with the principle of operation of an optical mouse. Flip the arm and view its optical system. Pay attention to the intricate detail that combines the lens and the prism. The prism is needed for the reason that the LED is located horizontally, and the light from it must be directed downward. Straight to the rug. The presence of a lens indicates that the mouse has a camera.
This chamber is extremely primitive. Its resolution is only 16 lines by 16 pixels. Half the size of a mechanical television camera of the early twentieth century. She periodically takes pictures of the texture of the rug, and a special microprocessor analyzes them. By the displacement of the texture, it determines in which direction the mouse was moved, and transmits information about this to the computer.
When the manipulator is moved, the pictures must be taken at great speed. In this case, the LED must be lit continuously so that the camera can take a picture at any time when it is required. If the mouse is stationary, you can take pictures of the rug less often. To conserve the life of the LED (and the battery charge, if we are talking about a mouse connected to a laptop or a wireless pointing device), you can make it not glow constantly, but blink quickly. So fast that it seems to the eye that it still glows continuously, but with less brightness. However, if you wave the mouse in this mode in the air, you will notice the stroboscopic effect. Scientifically, this method of dimming is called pulse width modulation.
If the mouse is not used for several minutes, the microprocessor switches the LED to an even more economical mode. He begins to periodically give short flashes. Their duration is quite enough to have time to take a picture and determine if the manipulator has been moved. If it turns out that this is the case, the microprocessor will immediately switch the LED to a constant light and force the camera to take pictures at a high frequency. But before this happens, there may be a short pause. Therefore, a mouse that has been idle for a long time may not start responding instantly to movements again - this is normal.
