DIY Laser levelling using webcam and laser level

[devmonkey]

Hi Bert and everyone,

Here are some renderings of the laser-plano-meter I've been trying to describe.


It consists of a square device sat on 4 spherical feet at the corners. 3 corners of the square are rigidly connected to form a triangle (orange part) with laser attached. The forth corner is attached by the green arms to the triangle with flexures that allow it to pivot up and down with respect to the triangular plane, effectively the square is allowed to fold along its diagonal. The camera sensor is attached to the forth corner.


The laser will project a line on the sensor, the height of this line is related to the angle of the fold. The goal is to find the sensor reading where ALL 4 feet are in the same plane thereby providing a method of measuring the error of any surface from a plane. We will call this sensor reading ZERO.

To find ZERO we place the device on any surface, doesn't need to be a plane. We then take the laser height measurement H1 in this position. Now rotate the device 90 degrees about the Z axis and replace it on to the same surface so that each foot is in the same place as its predecessor was in the first position. Now measure laser height H2.

With both H1 and H2 we can calibrate the device. ZERO is the mid point between H1 and H2.

Now place the device on the surface to be measured, e.g. the pair of X rail beds of the CNC frame. The deviation from ZERO will tell you how much to adjust the frame under the 4th foot in order to bring the surface into plane.

An alternative way to think of it is if you just placed the non-zero'd device on the machine frame and take the laser height measurement, then rotate 90 degrees and repeat, if the heights are different you need to adjust the frame. Make the adjustment, rotate the device back to its original position and repeat until the height readings match.

EDIT
Should be noted that this device could be constructed with a DTI instead of a laser as per a normal repeat-o-meter. In this case you would have just the orange triangle and replace the laser with a long arm with the DTI on the end. The problem of course would be that the error due to the long arm flexing due to its own weight and the pressure from the DTI spring would far exceed the resolution of the DTI. This is not a problem with the laser beam as it wont bend no matter how long it is.

Cheers, Joe

[driftspin]

Hi Bert and everyone,

Here are some renderings of the laser-plano-meter I've been trying to describe.


It consists of a square device sat on 4 spherical feet at the corners. 3 corners of the square are rigidly connected to form a triangle (orange part) with laser attached. The forth corner is attached by the green arms to the triangle with flexures that allow it to pivot up and down with respect to the triangular plane, effectively the square is allowed to fold along its diagonal. The camera sensor is attached to the forth corner.


The laser will project a line on the sensor, the height of this line is related to the angle of the fold. The goal is to find the sensor reading where ALL 4 feet are in the same plane thereby providing a method of measuring the error of any surface from a plane. We will call this sensor reading ZERO.

To find ZERO we place the device on any surface, doesn't need to be a plane. We then take the laser height measurement H1 in this position. Now rotate the device 90 degrees about the Z axis and replace it on to the same surface so that each foot is in the same place as its predecessor was in the first position. Now measure laser height H2.

With both H1 and H2 we can calibrate the device. ZERO is the mid point between H1 and H2.

Now place the device on the surface to be measured, e.g. the pair of X rail beds of the CNC frame. The deviation from ZERO will tell you how much to adjust the frame under the 4th foot in order to bring the surface into plane.

An alternative way to think of it is if you just placed the non-zero'd device on the machine frame and take the laser height measurement, then rotate 90 degrees and repeat, if the heights are different you need to adjust the frame. Make the adjustment, rotate the device back to its original position and repeat until the height readings match.

EDIT
Should be noted that this device could be constructed with a DTI instead of a laser as per a normal repeat-o-meter. In this case you would have just the orange triangle and replace the laser with a long arm with the DTI on the end. The problem of course would be that the error due to the long arm flexing due to its own weight and the pressure from the DTI spring would far exceed the resolution of the DTI. This is not a problem with the laser beam as it wont bend no matter how long it is.

Cheers, Joe

Yes, that really helped.

This is a clever design.

I will try this later. I think a simple laserpointer will do i guess in this scenario.


Thnx Grtz Bert.



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