Apparatus with two input beams for generating optical scans

An optical scanner for receiving an input beam and for generating an optical output beam which repetitively scans a fixed path comprising:

• a. means for converting the input beam into alternating first and second input beams lying within non-intersecting planes;
• b. a first polygonal mirror repetitively rotated through an angle about a first axis for receiving the first input beam and for repetitively generating a first scan;
• c. a second polygonal mirror repetitively rotated through an angle about the first axis for receiving the second input beam and for repetitively generating a second scan, said first and second mirrors having random facet to axis errors and a relative phase angle greater than zero;
• d. first means for redirecting the first scan back onto the first mirror to form a first redirected scan, said first redirecting means including a first reflecting surface lying within a first plane and a second reflecting surface lying within a second plane oriented perpendicular to the first plane, said first and second planes intersecting along a first line oriented perpendicular to the first axis and positioned between the first scan and the first redirected scan, wherein the first redirected scan is reflected from the first mirror to generate a plurality of first output scans which are directed through parallel, non-conincident paths, the first redirected scan being vertically displaced from the first scan by a distance related to the mirror facet to axis error and laterally offset from the first scan by a distance related to the relative angle between the mirror and the first beam and wherein the first and second planes are oriented such that a plane bisecting the included angle between the first and second planes is also oriented perpendicular to the first axis to generate linear output scans in response to the first input beam;
• e. second means for redirecting the second scan back onto the second mirror to form a second redirected scan, said second redirecting means including a third reflecting surface lying within a third plane and a fourth reflecting surface lying within a fourth plane oriented perpendicular to the third plane, said third and fourth planes intersecting along a second line oriented perpendicular to the first axis and positioned between the second scan and the second redirected scan, wherein the second redirected scan is reflected from the second mirror to generate a plurality of second output scans which are directed through parallel, non-coincident paths, the second redirected scan being vertically displaced from the second scan by a distance related to the mirror facet to axis error and laterally displaced from the second scan by a distance related to the relative angle between the mirror and the lower input beam and wherein the third and fourth planes are oriented such that a plane bisecting the included angle between the third and fourth planes is oriented perpendicular to the first axis to generate linear output scans in response to the second input beam;
• and
• f. means for converging the plurality of first and second output scans onto the fixed path such that the optical output beam from said scanner repetitively scans the fixed path thereby eleminating the effective of the facet to axis errors of the first and second mirrors and doubling the effective mirror scan efficiency.