PanoTools:
Re: entrance pupil - nodal point
Rik Littlefield 2004-Nov-11 19:13:28
--- In #removed#, "David Sykes" <#removed#>
wrote:
>
> Rik Littlefield wrote:
>
> > An alternate approach using a laser pointer is illustrated at
> > http://michel.thoby.free.fr/Liste-experiments1.html .
>
> What does he mean by rotating the laser around itself ?
> I don't quite understand the method.
> As he says, he seems to be locating nodal points, not entrance
pupils.
> The laser beam is presumably heading towards the 'anterior nodal
> point' (the front one !) and after refraction by the lens passes
> nicely through the entrance pupil.
>
> If someone can explain his method better, I will give it a go.
David,
As I understand Michel's experiment, he is just finding where the
laser must be pointed to get the most light through the lens.
Wouldn't that be the center of the entrance pupil?
I think that "rotating the laser around itself" just means making it
point farther forward/backward along the optical axis.
If you try this with your telecentric lens, I expect that the most
light will get through when the laser is pointed parallel to the
optical axis, no matter where the light enters the front element.
That would be consistent with pointing at the entrance pupil, way off
at infinity. I have no idea where the nodal points are for that lens.
--Rik
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