DIY Laser levelling using webcam and laser level

[John McNamara]

Hi Kitwin
Glad you got the software going, pity you are so far away From Melbourne.

Hi Devmonkey

This weekend I experimented with the tools I had to hand. An Aldi Cheapie Laser and the Microsoft webcam. I wanted to understand my tools better.

This session I left the lens on the camera and to avoid the distortion caused by the lens, I pointed the laser at a piece of flat finished black cardboard. I aimed the camera at the cardboard As you can see this cardboard caused the beam to appear very dim visually. However as the Graph below shows the camera responded very well to the beam. The software was able to discriminate the bright beam against a dark background very well. A nice sharp Gaussian peak was produced. i Am not sure what the white flecks are I grabbed the screen and each time they were in a different position They did not affect the resulting graph.

However the setup reminded me that using a lens will change the resolution of the device.

See the spreadsheet image below. For no particular reason I had placed the camera at a distance from the target that meant that the area covered was about 3.8 inches. This means that the 640 pixels of the image sensor will be divided over the 3.8 inches.

I used gauge blocks to measure a distance of 0.05 inches. a difference of about 8.4 pixel lines. This means that the setup as illustrated can not resolve more than about 6 thousandths of an inch.(I did not attempt to read more than 1 digit past the decimal point in the output box) The results were repeatable.

Clearly if a camera with a lens is to be used from wide angle to microscope the resolvable distance will be determined by the magnification power. A microscope would increase the resolution. As I am interested in wire alignment, using a lowish power microscope is worth consideration. Depth of field needs to be investigated.

Yes I knew this before but making a test brings it into focus. (Excuse the pun!) It also made me think on other applications that may benefit from a wider field of view at a lower resolution. As tested 6 thousandths of an inch resolution over 3.8 inches is excellent. EDIT There may be some lens distortion of the image and therefore the linear accuracy that would need to be taken into account.

My next tests will be with wire no lens.

Regards
John

Three images below.