DIY Laser levelling using webcam and laser level

[John McNamara]

Hi Kitwin

I would like to avoid a laser altogether. Instead ideally I would like to use the shadow of the wire over the sensor backlit with a dispersed light source. This would avoid any focussing issues. There would be a shadow formed on the sensor with a normal distribution characteristic darkest in the center. to lightest near the two edges.

Borisovs paper mentioned earlier uses omron sensors in this manner, no optics.

As the camera sensor is only about 2mm square. with .008" wire I can imagine that the workable measurement range would be about 1mm at best. This is where the device I made would help. It has a range of about 5mm, It could be used to center the sensor. Once this is done the current count of the stepper would represent the null point on the sensor.

These counts could be plotted along the wire giving a chart of the flatness of the object being measured.

For longer distances over a metre the catenary sag of the wire will become noticable. This can be computed as the measurements are taken along the wire assuming the drive is stepper or a servo with an encoder.

Alternatively glass optics, I guess however there are many hurdles to a perfect arrangement.

Note
One of the very practical reasons for using wire is that it can be positioned very accurately prior to measurements being taken. Both endpoints can be fixed and very accurately aligned to the surface being measured. and once fixed they stay put.

I also have a Taylor Hobson alinement telescope. It works well but not to .0001" of an inch. (.002" is achievable) Setting it up buy aligning the targets is no easy matter. An hour can easily pass. If a target is knocked you have to start again. pointing a laser will be the same. Using both systems there is no obvious error. It can only be found out by checking.

When I did work on my lathe I used stretched wire mounted at each end on the bed. Here I used a Microscope. A digital camera sensor should be a lot more accurate. Scroll down to near the bottom of the following link.

https://www.model-engineer.co.uk/for....asp?th=136771

Regards
John