DIY Laser levelling using webcam and laser level

[Michael Gilligan]

I think it worth sharing this FAQ answer from Edmund Optics:

Frequently Asked Question
Question

What is the difference between refractive and diffractive line generators?

Answer

A refractive line generator uses a cylinder or rod lens to focus a laser in only one axis only (drop-moved placement) in order to create a line of light. A diffractive line generator uses a flat optic with an etched microstructure that breaks apart a laser beam and forms an interference pattern in the shape of a laser line. Refractive optics do not correct for the inherent Gaussian profile of a laser beam and form a line with a "hot spot" in the center and fading edges. Diffractive optics will create a line that is uniform in thickness over its length, but is segmented. Diffractive line generators also cause a small portion of the light to be redirected into different diffractive orders, which causes additional faint lines to appear. Some laser line generators use a unique patented Powell glass lens design in order to achieve a continuous (not segmented) line with an even distribution along the length of the line.

Here is Powell’s patent:
https://worldwide.espacenet.com/publ...C&locale=en_EP

and a more comprehensible description:
https://www.laserlineoptics.com/powell_primer.html

MichaelG.