The M-DW1 wafer-mapping sensor is a perfect alternative to laser wafer-mapping solutions. By employing a safe LED light source, extra safety considerations that are associated with laser type products are eliminated. A two segment receiving element ensures accurate edge detection regardless of thickness or shape. Also, the wavelength band of the LED light source is wide enough to accurately detect a number of different wafer types such as glass or nitride-coated wafers. Lastly, the M-DW1 has a 0.5ms response time allowing use in high-speed operations.