Re: [tech-3d] fresnels & episcopes

[lunazzi <lunazzi@xxxxxxxxxxxxxx>]

I just repaired an old episcope and made use of it to project on a Fresnel lens 
about 20 cm wide and 25 cm focal length.
Because the image is focused very far from it by its original objective (FL= 36
cm), 
I added a second objective (FL 27 cm) in contact with the original.

I could see a 3D image at about 0,4 m distance from the lenses in 3D and a short
distance 
in front of the screen-lens.
But the field of view was very restricted.

Other combinations of objectives did not allowed both eyes to see at the same
time, 
so no 3D was available.

It is then when a holographic screen (15 cm wide and 30 cm tall, 30 degrees mean
diffraction angle) of my own allowed to see in a wider field of view,  being
confortable to the observer.

The diffraction effect affects the sharpness of the image in a similar way than
it happens 
in a white light holographic image: spectral blurring proportional to the
distance image-screen.
It affects the color also, loosing some fidelity.

I will try to put photographs or even videos at web in the future.

The apparatous has fan cooled halogeneous lamps for 1,3 kW, and it seems to me
that it could even burn if used for more than half an hour continuously.

Yours,

José


sergio baldissara wrote:
> 
> --- In tech-3d@xxxxxxxxxxx, "sergio baldissara" <winter@xxxx> wrote:
> > nice tip!!!
> > I'll try with small solid objects and an episcope. of course I'll
> > make you know.
> Done it... it didn't work (Josè Lunazzi already warned me off-list,
> and he was right). I should have imagined it would behave like
> fresnel screens of reflex cameras...
> Sergio


------------------------ Yahoo! Groups Sponsor ---------------------~-~>
eGroups is now Yahoo! Groups
Click here for more details
http://click.egroups.com/1/11231/1/_/520353/_/981743790/
---------------------------------------------------------------------_->