Automated photomask inspection apparatus

An optical inspection system, comprising:

• a stage for moving a substrate and including
• an X stage,
• a Y carriage in the shape of a frame to carry the X stage, the frame having two guideways,
• an X linear motor configured to drive the X stage and having
• a stator imbedded inside one of the two guideways at an angle to a wall thereof, and
• a slider separated from the stator by air bearings and arranged relative to the stator such that an attractive magnetic force is at an angle to each of the air bearings, and
• a Y linear motor configured to drive the Y carriage;
• a laser source for producing an illuminating light beam;
• a plurality of optical elements for focusing said illuminating light beam on said substrate;
• a beam deflector for scanning said illuminating beam across said substrate;
• a light detector for producing a signal representing changes in said scanned light beam reflected from said substrate;
• and
• electronic means for comparing said signal to a reference signal.