Flying spot scanning

Claim 1

In a flying spot scanner system of the type having: a. a multifaceted mirror adapted for rotation about its rotary axis, b. an infrared laser source of light, and c. means for beaming said light at said mirror for reflection thereof to a photosensitive web being scanned, the improvement wherein the said means for beaming said infrared light is adapted to focus said infrared light to a spot on the said element being scanned before said infrared light strikes the said mirror for reflection to the said photosensitive web, said system including means for so restricting the dimensions of the focusing beam striking the said mirror that only part of a mirror facet is illuminated during substantially all of the time that the said light is reflected to the element being scanned, the focused beam being so dimensioned that it illuminates approximately one-half a mirror facet during the time that such beam is wholly reflected from such facet, and the distance (D) of said mirror from said element being scanned being substantially as small as is necessary for the defined spot to be formed during scanning from substantially all of the infrared light beamed at the said mirror, a. photodetector means responsive to infrared radiation for detecting light from the said spot, b. lens means for expanding the dimensions of the output beam from said laser, and for focusing said beam via said mirror to a spot on the said photosensitive web being scanned, and c. means for providing an optical stop for blocking light from the said laser which is radially more than a predetermined distance off the optical axis of the said laser.