Hey All,

I need help figuring out how to project a very small image (about 2 cm x 2 cm). To start, I have a standard DLP projector. I'd like some advice about adding a lens or two to condense the image to the size of a postage stamp. Alternatively, I could toss out the projector, and just use a CRT or LCD monitor and a couple lenses.

I'm fairly new to optics, but I'm trying to learn. I think that this will involve picking lenses with the right focal length and such. The DLP projector is a bit of a black box optically. I might spend some time trying to reverse engineer what its focal length is...

If you wondering, my application involves stimulating light-sensitive neurons in a petri dish. The neurons respond to flashes of blue light.

Thanks much,
Tom

hi and welcome to lumen lab
this is the easy way out
make a hole in a box (you will have to experment withe the right size hole) so a 2 cm^2 box will apear
i am new to optics as well just that the light will not be very concentrated

This is actually kind of a tall order.

Projectors are designed to enlarge the source image, not to shrink it. Making this happen from a projector will be tricky.

What kind of resolution do you need?

As a suggestion though, I would use a regular LCD, and a camera lens. Since a camera lens is intended to focus onto 35mm film, it will be excellent for a 2cm by 2cm image field. Focus the camera lens on an LCD, and put the petri dish where the film would go. It's VERY short throw, like the size of a 35mm camera body.

Ideally, you'd want a macro photography lens.

Then, depending on how much light you need, you just need to increase the brightness of the LCD.

Thanks for the welcome, and for the helpful thoughts.

The projector is 1024 x 768 pixels. I'm hoping to get the resolution in the range of 15 microns per pixel. That way each cell would be a pixel or two wide. The camera lens is a really good idea--I hadn't thought of that. I'll give it a shot. Luckily, my lab has a camera with a macro lens that focuses from 30 cm to infinity. I'll try using it to collect light from an LCD monitor, or a CRT if I need more power. I report back as soon as I try it.

I appreciate all the ideas. As a side note, I'm going to use Processing, an easy graphics software environment, to control the display. It can update each frame, but occasionally it blips. I wish I could more precisely control the timing, and also have faster timing. Maybe I'll use a high speed shutter of some sort. Hmm. Ideally, I'd be able to get down to 1 or 2 milliseconds.

Thanks again,
Tom