Demonstrating a pinhole camera with a screen projector

[DrToby]

Does anybody have experience with using a electronic screen projector to simulate the (sunlight illuminated) outside world to image it through a small pinhole? The basic experimental setup would consist of i) a blank screen, ii) a vertical cardboard with a small hole and iii) a screen projector that shows an still image and/or text. Anybody any ideas how to didactically execute this experiment?

 

[Steve4Physics]

Does anybody have experience with using a electronic screen projector to simulate the (sunlight illuminated) outside world to image it through a small pinhole? The basic experimental setup would consist of i) a blank screen, ii) a vertical cardboard with a small hole and iii) a screen projector that shows an still image and/or text. Anybody any ideas how to didactically execute this experiment?

Immediate (and probably not that helpful!) thoughts are...

Have you attempted a trial-run to see if you can get it to work? If you look into a projector, you don’t see the image that’s being projected. So, from the viewpoint of an ‘observer’ at the pinhole, the directions of the incident light-rays are not what are required for a pinhole camera to work. I think a useful image would not form on the screen.

The proportion of the projector’s output passing through the pinhole would be very small, so only a faint image (if one is produced) would be created on the screen.

Its quite easy to do pinhole camera demo’s without a projector – using the outside world. Or even a bright bulb in a dimmed room. Is there some specific reason for wanting to use a projector?

Even quite young pupils can, with simple guidance, make and use their own pinhole camera, e.g. during a lesson or as a homework task. YouTube has videos.

Good luck!

 

[Andy Resnick]

Does anybody have experience with using a electronic screen projector to simulate the (sunlight illuminated) outside world to image it through a small pinhole? The basic experimental setup would consist of i) a blank screen, ii) a vertical cardboard with a small hole and iii) a screen projector that shows an still image and/or text. Anybody any ideas how to didactically execute this experiment?

I did not use a screen projector, but a colleague and I set up a camera obscura using an empty room (with a window). The demo worked really well, we had a couple of the intro classes come into the room and experience it.

It took some work: the room had to be completely light-tight with a small hole (about 1/4 inch) in the window covering. This is what the viewing screen looked like- notice the image is inverted.

The yellow light is the residual light leak... If you want to try this, you need (nearly) complete darkness and time for everyone's eyes to adjust. It's a great demo!

 

[Drakkith]

As has been said, you can't use the projector itself to shine on the cardboard with the hole. You'd only get a small portion of the image coming through. Your best bet is probably to use a window on a bright day to get a view of the outside world.