Quote:
Chrisbee wrote:
 I think your mirror would have to be large to remain in the beam at any reasonable excursion. |
Depends on what you consider large, at a 45 degree angle to the laser the mirror diameter will have to be at least the same as the excursion to be measured. So for +-20mm, you'd need a mirror that is at least 40mm in one direction.
Quote:
Chrisbee wrote:
Your target would have to be translucent or transparent to make the beam visible. The beam would then be capable of eye damage. |
Well not really, the scale can (in theory) be any distance from the sub so one can fit between them to read the scale.
Quote:
Chrisbee wrote:
Collo's idea has more merit in that it will record any excursion. The downside is having to attach an extended object to the dustcap. This makes the driver and reflector stalk too vulnerable. IMO. |
Fix the laser at a 45 degree angle and the scale perpendicular to the mirror and you'll get a reading that is double the excursion. Just divide the number by two and you get your result.
I drew it on paper to see if it works.
Here's it: