effect of distance

Derek Robson

The beams look like they are not parallel between zero and 1st order. But I thought that’s the way the physics worked – the light is diffracted through an angle relative to the incident light.  I’ve done a series of repeatability tests by firing LASERs at roof tops and aerials (in the dead of night) and will be looking at the spread of the distances from the zero order. But this is on dots, not the beams.  I’m looking at the target as the source of the LASER light coming back to the sensor. Some images on the wide angle lens show the beams at angles. But we know even parallel roads will join together in the distance (perspective).  I’m measuring the position of the diffracted dot relative to the zero order dot. That should show if there is any non linearity in the wavelength range I guess.  Another problem is, the diffraction gratings are plastic, so they are not rigid, and can bend, causing curved spectra (curvature along the wavelength axis). But despite that variation, I hope that will be insignificant and not interfere significantly, or at all, with identifying elements.