Scanner having a misalignment detector

A laser scanning device, the device comprising:

• a spinner for scanning a light beam having a light spot across a scanning line;
• one light spot misalignment detector located generally at a beginning of said scanned line for measuring an initial misalignment of said light spot in a cross-scanning direction;
• and
• a beam misalignment corrector which, during scanning along said scanning line, dynamically corrects scanning misalignment of said light beam in accordance with at least said initial misalignment,
• wherein said spinner comprises a plurality of facets and wherein said beam misalignment corrector additionally includes means for correcting in accordance with the current operative facet,
• and wherein said beam misalignment corrector additionally comprises a smoother for moving said light beam from a final location of a current scan line scanned with a current facet of said spinner to a first estimated location of a next scan line, wherein said first estimated location is the value of the pre-position signal measured when the next facet was last utilized.

A laser scanning device, the device comprising:

• a spinner for scanning a light beam having a light spot across a scanning line;
• one light spot misalignment detector located generally at a beginning of said scanned line for measuring an initial misalignment of said light spot in a cross-scanning direction;
• a beam misalignment corrector which, during scanning along said scanning line, dynamically corrects scanning misalignment of said light beam in accordance with at least said initial misalignment,
• wherein said beam misalignment corrector comprises:
• a pre-positioner which determines a pre-position signal which offsets said initial misalignment;
• estimation means for producing, from at least said pre-position signal, an estimated scanning misalignment;
• and
• a beam shifter responsive to said estimated scanning misalignment for shifting said light beam thereby to correct said scanning misalignment,
• and wherein said pre-positioner comprises a closed loop control system controlling said beam shifter and operative to generally cancel said initial misalignment.

A method of laser scanning, the method comprising the steps of:

• reflecting a light beam having a light spot across a scanning line;
• measuring an initial misalignment of said light spot in a cross-scanning direction;
• and
• during scanning, dynamically correcting scanning misalignment of said light beam in accordance with at least said initial misalignment,
• wherein said step of producing comprises the steps of:
• estimating a first portion of said scanning misalignment due to pyramidal error and to an extent of wobble present at the beginning of said scanning line;
• estimating a second portion of said scanning misalignment caused by said wobble;
• and
• summing said first and second portions with said pre-position signal.