need some help (optics.....)

[yanir89]

Hello everybody. My name is Yanir and I'm from Israel.

Before I begin I want to apologize for my shallow level of language.

 

I have an idea to build a portable slide projector which made up of a flashlight, a transparency with a picture on it, and a few lens.

 

The point is- that I'll be able to show some pictures on a wall with this portable flashlight.

 

There is an example of the idea-

http://img204.imageshack.us/img204/4647/dsc01895uf1.jpg

 

I hope that you can help me.

 

THANKS!

[yanir89]

ive just found something interesting.

( http://www.sz-wholesale.com/p/projector-flashlight/projector-flashlight-30591.html )

 

the only difference is that i need the pictures to be in a higher quality....

 

 

thanks again

[timo]

Nice sketch. Since you´ve not asked a question I am not really sure what kind of replies you´re expecting.

 

Apart from issues with the level of detail you can achive, the most striking problem that comes to my mind is the amount of light you need. If it´s supposed to work in daylight, then I am not sure that a normal flashlight will give you enough light for the picture to be well visible. Beamers tend to have specially-bright lamps in them that also need special handling (e.g. you cannot simply plug off a beamer after use but instead need to let the cooling work for some more time after use). Beamers also are portable, at least to my understanding of the term (i.e. they are roughly the size of the laptop I plug onto them).

 

If you simply take a flashlight and shine through some transparency/dia on a wall you´ll see the tranparency projected there. What do you want to change/improve/... ?

 

Btw.: Welcome to these forums.

[yanir89]

First of all, thank you for answering.

 

In order to make it as simple as possible, let's say that it isn't supposed to work in daylight.

 

I want to say that the projector's purpose is to show pictures like- me and my friends or things like that, and therefore the projector must display the pictures in a good quality.

 

I think that the level of quality is most affected from the way I print the pictuer on the transparency. SO, should a standard printer produce such a pleasant quality?

 

 

(again- Im sorry if my language makes it hard for you to understand me..)

[Rocket Man]

quit apollogising, you have better grammar than most people on this site.

 

if you have a printer that will make a projector-quality print for an overhead projector, you'll get a projector-quality image.

the bigger the print is, the more resolution you can cram into the image resulting in a better projection.

 

the only things you need to watch out for is the focussing. if you have a simple point source, like a bare light bulb from a torch, you'll get a very crisp image.

if you use a large, frosted-glass light bulb, you'll get a fuzzy one.

 

the best i can suggest is a bulb from a car's headlamp running high beam without a reflector.

a reflector would make the image brighter but it would need to be a sphere wrapped around the bulb otherwise, you'll get a blurred image.

 

you might be able to silver the inside of a christmas bauble, cut a hole in the bottom and mount the headlamp in the centre, pass the light through the image and onto the wall.

[YT2095]

or you could use those hyper-bright white LEDs, they do up to 4000MCD now

[yanir89]

Thank you guys.

The first thing I'm going to do is- to print some pictures in different sizes, and then I'll try some flashlight Ive got.

 

I hope that it's going to be simple....

 

 

p.s. for my printings I'll use my HP 6110 (all-in-one) printer....

[Klaynos]

The smaller the 'slide' (transparancy) you illuminate the higher the resolution will need to be, and also the larger your light beam will have to be where it hits it.

 

The car headlamp idea is a good one imo. I'd have thought most tourches are too narrow beamed.

[Rocket Man]

the "narrow beam" will really mess up the image. you need a good strong point source to get a crisp image. also, the images will be printed square on a flat surface. when the light hits the wall from a point source, it will come out square and crisp. if it gets magnified along the way, it wont be square and if it's not a point source, it will be completely blurred.

[Jacques]

Why not simply use a lens between the transparency and the wall ???

[Rocket Man]

like i said, most lenses you're going to find will distort an image, best save the lenses etc for behind the transparency.

[Jacques]

It's easy to find an achromatic lens who will give a better definiton than a pin point light source. With a lens, you won't need a pinpoint source, just need any light source with a frosted glass to distribute the light evenly. When I was a kid, I build a projector like that and the key factor to minimize distortion is by having the maximum focal lenght, but that reduce magnification...

[Rocket Man]

nothing will give better definition than a "pin point light source" also, nothing is simpler to build or get parts for. a pinpoint source gives mathematically null distortion, zero spectral dispersion, and far less hassle in constrution.

 

if you scale up, a lens will be necessary to keep the sixe of the projection practical. if you move the projector further back, the lamp must move back proportionally, but it gets to a point where the light dwindles too much, at that point, you'll need to look at lenses.

[Jacques]

nothing will give better definition than a "pin point light source"

I don't know why you belive that.

Let take a simple example.

Let say the pin point source is 1mm diameter and the transparency is 10cm from that source and the screen at 1m from the source, then a detail of 0.1mm on the transparency will be on the screen 1cm+0.1mm. It is easy to get better with a simple lens.

[Rocket Man]

good point, modify the source, force it into the definition of "pin point". i'll still suggest grunge tech though. the headlamp reflector and a magnifying glass. parralel rays WILL focus into a 0 diameter point if you buy a decent glass. this arrangement also has more power and a more "white" light than most available bulbs.