Helical scanning apparatus with one or more rows of scanning elements and an object of scanning disposed at an angle to the axis of a rotating drum to eliminate skew of scanning lines

摘要

A rotating-drum scanning apparatus includes a rotating drum and a feed mechanism for feeding a rectangular sheet to the drum and winding it around the drum so that one side of the sheet is inclined at an angle theta to the axis of the drum. In a first embodiments, a scanning head is disposed to be movable in a direction parallel to the axis of the drum and includes a plurality of scanning elements arranged along a line parallel to the axis of the drum. These elements form on the sheet scanning lines extending at right angles to said one side of the sheet as the drum and the scanning head move. The angle theta is given by theta =tan-1 DELTA L/L, where L is the circumference of the drum and DELTA L is the distance covered by the scanning head while the drum makes one revolution. Another embodiment is similar to the first embodiment except that it arranges the scanning elements along a line which is also inclined at the angle theta to the axis of the drum while the scanning head moves in a direction parallel to the axis of the drum. A third embodiment is similar to the second embodiment except that the scanning head also moves in a direction inclined at the angle theta to the axis of the drum. Yet another embodiment is similar to the first embodiment except that the scanning head has a plurality of rows of scanning elements, with these rows being spaced from each other in a direction perpendicular to the axis of the drum.