Re: Little Mouse

[mjmahon@aol.com (Michael J. Mahon)]

Wayne Stewart wrote:

>Bill Garber wrote:
>
>> I find that in a pinch a nice 24# sheet of printer
>> paper works very well as a mouse pad. And you can
>> print a pattern for your optical to follow on the
>> upper half, then fold. I do that when my present
>> pad is too dirty to catch the ball and I just fold
>> it in half, lay it over the pad I have and it works
>> great until I can get out to pick up or order a new
>> mouse pad. Try it. You may be pleasantly surprised.
>
>Um, the Little Mouse is one of the early optical mice. There is no
>ball and it doesn't work using paper as a mousepad. It needs
>something more reflective with alternating dark so black print on
>aluminum works but paper or regular mousepads don't. The little Mouse
>originally came with a special mouse pad as ordinary ones don't work
>with it.

The early optical mice did not do texture tracking as the current
generation does.  Instead, they had optical encoders driven 
directly by the image of the mousepad underneath.

Mouse tracking was determined by the orientation of the
pad, not the mouse, within a range of several degrees.

This requires that the mousepad contain a grid of horizontal
and vertical lines, spaced appropriately for the encoders and
of about 50% reflective-to-nonreflective ratio (that is, the lines
should be about as wide as the spaces between them).

To provide a cleaner signal, the pattern was usually made
of two different "colors", which would allow filtering in the
mouse to make the vertical lines almost invisible to the
horizontal encoder and vice versa.  (The "colors" often
extended into the infrared, since LEDs and optical sensors
work well there and have less competition from room light).

To further improve signal-to-noise ratio, the grid pattern
was applied to a smooth, reflective surface, usually aluminum.
A transparent film was on top for durability.

High-resolution mice (common with workstations) used a
relatively fine grid, while lower resolution mice used a coarser
pattern.  The A+ optical mouse used a relatively coarse pattern.

In principle, one could print a suitable pattern on mylar or on
a transparent film that could be applied to an aluminum plate.
In practice, it might be difficult to get the horizontal and vertical
rulings the right "color" and transparency to get smooth tracking.

Your best bet is to try to find one of the original plates, or
one that is similar enough to work.  ;-(

-michael

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