Has anyone seen this type of computer mouse?

This computer mouse IS NOT an opto-mechanical mouse, it has NO tracking wheels for x and y axis whose movements are detected by an optical sensor, (so nothing can get dirt on it but the ball itself.) this mouse has a more standard optical mouse sensor except instead of reading the surface, it reads the movement of the ball DIRECTLY, the ball itself has a pattern on it that makes it easy for the sensor to read. I saw it in a popular science magazine a few years back, What is this mouse called? what company used to make it?