Finding the Center of a Laser Dot

Apertures that create round laser dots also create diffractive rings around the laser dot which looks like target bullseyes.  The center of the target bullseye is the resized laser beam.  But these apertures do one other thing that’s necessary.  They block the majority of the laser light so that the center of the laser dot can be seen and marked by the person looking at the laser dot closely.

Humans look at round things quantitatively.  This means that the center of a laser dot is determined by looking at the top, bottom, left and right edges of the laser dot in order to average the distance between these edges.  But you have to see the edges.  If the laser dot is too bright, the edges can’t be seen.  Remember, laser light is coherent (all the same color) which means that the light looks like its boiling and unsteady.  So, blocking most of the laser light and using the right size aperture helps with marking the center of the laser dot.  Resolution determines accuracy and the smaller the laser dot the better the resolution.  Laser Tools Co. includes 1/16”, 3/32” and 1/8” apertures within their AP15 and AP16 Aperture Packs.  This system of beam resizing and quality is one of the most important benefits when using a laser beam as an effective reference between two points for alignment.