I'm somewhat new to creating projectors- I built one of those fresnel-box things and had marginal success with it. I had to completely darken my room, and in order to correct the image I projected onto the back of a sheet, which further lowered the image quality. Everyone in my dorm loved it, but I want something more. I've begun collecting parts for a nicer lcd based projector, but I wanted to ask some questions.
I've seen several different options, the most interesting to me of which is essentially a variation on the fresnel, where you bascily add some more lightbulbs to the inside of the box, use a mirror and a triplet lens insead of projecting into the fresnel, and voila. Has anyone tried this method? It would seem to me that the glare would make the image look very washed out?
Another option I'm looking at is the classic take-off the backlight approach, but space is a major concern for me. I saw a thread about a lilliput proj. which has a condensor placed in very close proximity to where (I think) the bulb is supposed to be loaded. What exactly is the function of a condensor lens and how do I determine the dimensions for its position in relation to the rest of the projector setup?
Thanks a bunch guys!
I've seen several different options, the most interesting to me of which is essentially a variation on the fresnel, where you bascily add some more lightbulbs to the inside of the box, use a mirror and a triplet lens insead of projecting into the fresnel, and voila. Has anyone tried this method? It would seem to me that the glare would make the image look very washed out?
Another option I'm looking at is the classic take-off the backlight approach, but space is a major concern for me. I saw a thread about a lilliput proj. which has a condensor placed in very close proximity to where (I think) the bulb is supposed to be loaded. What exactly is the function of a condensor lens and how do I determine the dimensions for its position in relation to the rest of the projector setup?
Thanks a bunch guys!
bigedizzle,
Check out Lumenlabs and DIYprojectorcompany for basic designs and information. Also read the two big long permanent threads at the top of the page. Also Mathias light engine permanent thread is good in lighting and optics forum.
Check out Lumenlabs and DIYprojectorcompany for basic designs and information. Also read the two big long permanent threads at the top of the page. Also Mathias light engine permanent thread is good in lighting and optics forum.
Yeah, I've gotten the basic design figured out. My primary concern is, as I said, space. I was looking at the aspherical condensers available from edmund optics.
Although edmund optics and other sites have described the function of a condenser loosely as "something that gathers light and projects it through the object/stage into the projection lens".
Good enough for government work, but, I can obviously use different optical components as a condenser. For example, I can use a fresnel, or an aspherical condenser. The aspherical condenser occupies less space.
So, my question is, I want to use the aspherical condenser, but the exact optical properties of such a lens are difficult if not impossible to find.
I saw someone use one where they placed the condenser at the focus of a parabolic reflector. I also saw a project which, from the photos, appeared to have only one condenser lens and no other reflectors or condenser lenses.
So what gives? Any tips on a small setup?
Although edmund optics and other sites have described the function of a condenser loosely as "something that gathers light and projects it through the object/stage into the projection lens".
Good enough for government work, but, I can obviously use different optical components as a condenser. For example, I can use a fresnel, or an aspherical condenser. The aspherical condenser occupies less space.
So, my question is, I want to use the aspherical condenser, but the exact optical properties of such a lens are difficult if not impossible to find.
I saw someone use one where they placed the condenser at the focus of a parabolic reflector. I also saw a project which, from the photos, appeared to have only one condenser lens and no other reflectors or condenser lenses.
So what gives? Any tips on a small setup?
I don't think aspherical condensers will reduce the size of a pj. A normal spherical lens is not perfect, its light focusing properties are limited. This limitation is called spherical aberration. An aspherical lens has had this limitation corrected but only when it is used at its focal length. Its greatest advantage is that it can collect light more efficiently.
DJ
DJ
Bigedizzle,
Have you checked out Ace's small projector. It's based on the Lilliput 7 inch LCD. This is about as small as you can get and still have a high quality picture with a DIY projector.
The other option for an even smaller projector is to find a large used 9 or 8 inch CRT lens. These lenses have very high light throughput and are designed so that the image is very close to the lens. With the lens covering the whole LCD, which would be the case if you had a 7 inch lilliput LCD you can have a very small and compact light engine. This is a very efficent design. And if you could find a lens would be very high quality.
Hezz
Have you checked out Ace's small projector. It's based on the Lilliput 7 inch LCD. This is about as small as you can get and still have a high quality picture with a DIY projector.
The other option for an even smaller projector is to find a large used 9 or 8 inch CRT lens. These lenses have very high light throughput and are designed so that the image is very close to the lens. With the lens covering the whole LCD, which would be the case if you had a 7 inch lilliput LCD you can have a very small and compact light engine. This is a very efficent design. And if you could find a lens would be very high quality.
Hezz
Heya there Hezz, great to see you back mate😉 I hope all is great.
Dazzla hit it prety much on the head there.
If you want to use an aspherical condenser system in your projector, buy some aspherical frensels. Trying to find or buy an aspherical glass lens for a 7inch lcd would not only have to be custom made but would cost an absolute fortune!! They have to also be bigger then the lcd.
I use an aspherical in mine, though not where the frensels are, mines used as a primary condenser, and this alone makes a very big diff when it comes to aberations even though my frensels are just standard pcx type.
Trev 🙂
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