Homebrew PCBs

On Fri, 14 Jan 2005 11:31:29 +1100, Adam Seychell  
<a_seychell@...> wrote:

>
>>
> Do you what the basic arrangement of the optics should be ? I  did a
> very simple experiment with some odd lenses I have (from microscope eye
> pieces). Trying to get any kind projection seemed futile.

Oh i get very good porjection already, on my test setup.
I used the convex lens, the picture close to focal point (but i don't  
remember if just outside or just inside). then the projected image will be  
sharp at a given distance, what that distance is is determined by how  
close to the focal point you are.

You can draw the optic path. draw a lens, a small arrow on the left. one  
ray goes straight from the tip of the arrow to the lens center, the other  
one goes parallel with the horizon through the lens (which deflects it  
through the focal point on the other side. You see, to make them intersect  
on the other side of the lens (sharp picture) you need to be just outside  
the focal point. By moving the small arrow you can move the size and  
position of the big one. Once you come as close as, or closer than the  
focal point the picture diverges and does no longer project.


ST


> I tried both convex with flat and double convex lenses. The projection
> screen was transparent plastic film with diffuse coating. I could not
> get any close range image projected into the screen any any amount of
> light. The only way I could see reasonable images was looking at objects
> at infinite distance, or greater than few meters distance.
> If my thinking is correct, wouldn't a converging lenses need some type
> of very small aperture to get a sharp image projection ?
> Adam