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I have to measure the variation of a wide angle laser beam divergence. I would like to avoid the use of lenses and/or attenuators.
I was thinking to project the laser beam on a screen and to put a camera on the laser side to take a picture of the ellipse projected on the screen. It would be enough to measure the two axis diameter without using attenuators or lenses.

Would it work? Do you have any suggestion?

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This is a viable method but not necessarily extremely accurate.

First, you'd want to mark a scale on the screen to be able to read the beam width from the images captured by the camera.

Second, you'd need to know that the camera sensor has very linear response, uniform across its sensor, to be able to determine the point in the image where the beam intensity has dropped by half.

Third, you'd want to be sure the screen produces very uniform and entirely diffuse reflection (minimal or no specular reflection), so that the image seen by the camera accurately indicates the beam intensity at all emission angles.

Finally, you should realize that this method does not "avoid the use of lenses" since the camera certainly uses a lens to image the screen onto its sensor.

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