Optical system for determining peripheral characterization and dimensions of a sheet

A plurality of lights are mounted relative to one another to direct light beams toward a glass sheet along continuous scan portions. The sheet moves through the scan portions to reflect light beams toward a linear array of diodes. The linear array of diodes is activated and deactivated to simulate a discrete scan path and to generate points of intersection between the edge portions of the glass sheet and the scan path. The signals of the photodetectors are acted on to determine peripheral characteristics of the sheet such as squareness of the corners, linearity of the sheet sides and length of each sheet side.