Importance

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Abstract

A system and method for correcting a scan pattern of a moving optical scanning system. A gantry moves an optical system at a constant rate in a first direction. Using a light source and a first deflector, the optical scanning system quickly sweeps a light beam in a direction orthogonal to the motion of the gantry by changing the angle of deflection of the first deflector linearly with time. To compensate for the motion of the gantry, the optical system includes a second deflector which deflects the light, the deflection angle being determined as a function of the velocity of the gantry. The deflected light is focussed on the object (or pattern). Accordingly, the object is scanned along a corrected scan line orthogonal to the X-axis. The optical scanning system may optionally perform 'selected' scanning. Also, the optical system optionally employs a 'look-ahead/look-behind' scanning approach to further improve the rate at which portions of an object (or pattern) may be inspected.

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First Claim