Quote Originally Posted by John McNamara View Post
Hi Joe

The line generated should be straight if the laser is located perpendicular to the axis of rotation. if not on axis a slightly curved line would be generated.

The bearings of the rotating spindle may not be perfect, this may cause the edge of the optical plane generated to wobble up and down for each rotation turn? However your software makes multiple measurements and averages them, This should help cancel out this error.

Regards
John
Hi John,

A penta-prism doesn't suffer this problem, it has two faces at 90 degrees, then two other faces at 90+22.5 to the first two, the fifth face is not relevant, some might not even have it or maybe have multiple. Good picture on wikipedia.