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A Scanning System including Adaptive Optical Components Disclosure Number: IPCOM000005837D
Publication Date: 2001-Nov-11

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A laser scanning system including an adaptive optical element operative to introduce a predetermined aberration into the wavefront of the laser beam as a function of the location of the laser beam in its scan direction. By suitably deforming the wavefront, the system corrects aberrations introduced by the systems optical components, thereby enabling increased resolution.

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                FIELD OF INVENTION The present invention relates generally to scanning systems and more particularly to optical correction in laser scanning systems employed in the inspection or laser direct imaging of electrical

circuit patterns.

                 BACKGROUND It is known to employ scanning laser beams in systems used to inspect electrical circuit patterns deposited on substrates and to expose electrical circuit patterns in photosensitive coatings



on electrical circuit substrates. In such scanning systems, typically it is desirable to scan a field with a spot whose optical properties (size, shape, wavefront configuration and the like) is substantially uniform over the entire field.

The maintenance of uniform optical properties of the spot over an entire field typically demands very tight design and manufacturing tolerances for optical subsystems, particularly with

respect to distortion, chromatic aberration, field flatness, telecentricity and the like. As the resolution requirements of scanning systems increases (and spot size decreases), increasingly tighter design and manufacturing tolerances are required in order to maintain uniform optical properties of the spot over the entire scanned field.



             SUMMARY OF THE INVENTION The present invention seeks to provide a scanning system having improved uniformity of spot size, and/or spot shape, over the extent of a scanned field.

In accordance with general aspect of the invention an aberration is introduced into a scanning light beam as a function of a location, a time or a sensed optical property of a spot


produced by the beam when projected onto a medium. Preferably the light beam is a laser beam. Alternatively or additionally the light beam is a coherent light beam. Alternatively or additionally, the light beam is employed in a diffraction limited scanning system, such a system used in the inspection of electrical circuits, or in a system used in the laser direct imaging of electrical circuit patterns.


Page 2 of 17

    In accordance with another general aspect of the invention, a laser beam scanning system is provided with a adaptable optical component operative to introduce an aberration into a scanning laser beam to change an optical property of the beam during scanning. Typically the aberration affects a wavefront configuration of the beam. Preferably the aberration is introduced is a function of the location of the laser beam in a direction of scanning, however the aberration may be

introduced as a function of time or a sensed property of the beam, such as spot size and shape. Preferably, the aberration is introduced with an adaptive optical element, for example a non-imaging element such as an optical microelectromechanical system (optical MEMS or MOEMS).

In accordance with another general aspect of the invention, one or more optical propertiesof a laser beam spot, such as its size, shape or wavefront configuration, are detected a...