Method and apparatus for alignment of scan line optics with target medium

Positioning of a scan line (L) relative to a recording medium drum (15) of a polygon printer is established by independently adjusting blocks (35, 36) mounted on a scan line generating optics module (10). The blocks (35, 36) have inverted V-notches (38) that nest in two-point tangential contact onto cylindrical surfaces of drum bearings (33, 34). X, z, ϑx and ϑz positions are set by x and z direction adjustment screws (44, 45, 49, 50) mounted on frame (11) that move against blocks (35, 36) against the bias of springs (61) and the weight of the frame (11). Clamping screws (56, 57) pass through oversized holes (58) and z direction elongated slots (59) on blocks (35, 36) to releasably lock blocks (35, 36) after adjustment. Alignment of holes (58), slots (59) and notches (38) maintains a constant angle of incidence during adjustment. A notch (41) of projection (40) of frame (11) engages with a pin (42) on printer body (29) to set y and ϑy positioning.