The development of the modern optical mouse at Hewlett-Packard Co. One refinement would be accelerating the correlation process by using information from previous motions, and another refinement would be preventing deadbands when moving slowly by adding interpolation or frame-skipping.

Its sensor would normally share the same ASIC as that used for storing and processing the images. Optical mice mathematically process these images using cross correlation to calculate how much each successive image is offset from the previous one.ДЄn optical mouse might use an image sensor having an 18 Г— 18 pixel array of monochromatic pixels. Depending on how fast the mouse is moving, each image will be offset from the previous one by a fraction of a pixel or as many as several pixels. Optical mice capture one thousand successive images or more per second. The amount that the edges of one photograph overhang the other represents the offset between the images, and in the case of an optical computer mouse the distance it has moved.

Place both photographs on a light table to make them transparent, and slide one across the other until their images line up. To understand how optical flow is used in optical mice, imagine two photographs of the same object except slightly offset from each other. Images of these surfaces are captured in continuous succession and compared with each other to determine how far the mouse has moved. These surfaces, when lit at a grazing angle by a light emitting diode, cast distinct shadows that resemble a hilly terrain lit at sunset. Optical mice use image sensors to image naturally occurring texture in materials such as wood, cloth, mouse pads and Formica. A simple binary-image version of digital image correlation was used in the 1980 Lyon optical mouse. The technology underlying the modern optical computer mouse is known as digital image correlation, a technology pioneered by the defense industry for tracking military targets. S5085 optical sensor IC die (CMOS sensor + driver) Other manufacturers soon followed Microsoft's lead using components manufactured by the HP spin-off Agilent Technologies, and over the next several years mechanical mice became obsolete. It worked on almost any surface, and represented a welcome improvement over mechanical mice, which would pick up dirt, track capriciously, invite rough handling, and need to be taken apart and cleaned frequently. The first commercially available, modern optical computer mice were the Microsoft IntelliMouse with IntelliEye and IntelliMouse Explorer, introduced in 1999 using technology developed by Hewlett-Packard. A surface-independent coherent light optical mouse design was patented by Stephen B. This advance enabled the mouse to detect relative motion on a wide variety of surfaces, translating the movement of the mouse into the movement of the cursor and eliminating the need for a special mouse-pad. As computing power grew cheaper, it became possible to embed more powerful special-purpose image-processing chips in the mouse itself.

Modern surface-independent optical mice work by using an optoelectronic sensor (essentially, a tiny low-resolution video camera) to take successive images of the surface on which the mouse operates. Microscope photograph of the IntelliMouse Explorer sensor silicon die The Kirsch and Lyon mouse types had very different behaviors, as the Kirsch mouse used an x-y coordinate system embedded in the pad, and would not work correctly when the pad was rotated, while the Lyon mouse used the x-y coordinate system of the mouse body, as mechanical mice do. Lyon of Xerox, used a 16-pixel visible-light image sensor with integrated motion detection on the same nвЂ‘type ( 5 Вµm) MOS integrated circuit chip, and tracked the motion of light dots in a dark field of a printed paper or similar mouse pad. Predictive algorithms in the CPU of the mouse calculated the speed and direction over the grid. One of these, invented by Steve Kirsch of MIT and Mouse Systems Corporation, used an infrared LED and a four-quadrant infrared sensor to detect grid lines printed with infrared absorbing ink on a special metallic surface. The first two optical mice, first demonstrated by two independent inventors in December 1980, had different basic designs: An early Xerox optical mouse chip, before the development of the inverted packaging design of Williams and Cherry

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