DIY-Projector Plans and theory collection !!

[Varonis]

Helo,

there I draw an idea, for replacing the first fresnel with right shaped reflector:

http://buildart.lv/Faili/paraboliks.gif

-- the reflector are taken from Satelite antenna (the stuff what catches tv signal from satelites, without any tech, but with its special lever who holds the lamp in precision focus point, that the reflected light makes a paralel beam. and i place aluminium foil, inside, to make better reflection, than original white matte coating.

this i have not tested in projector, but i tested it with 500W conventional light bulb - the results vere fantastic - we get a light beam, and we can hit the clouds with this light beam! - so, i decided that it works - light beam are parallel. so it is the same what first frensnel does. and many comercial projectors dont have the first frensenl so, they have a reflector what makes paralel light beam.

the fresnel are absorbing the light, but good reflector will be absorbing much smaller percent of light, so, we wil get brighter images?

sory for my bad english

[cromaclear-crt]

did you ever try this with a projector ?

[vandevoordekoen]

Hello, I now this tread is closed for a wiile, but is there anybody who tried de elliptical reflector setup? And where are those elliptical reflector to find? Thanks.

[giorgos18]

ywh has ellipsoidal reflectors for sale but they will not be suitable for standard MH, need to use the small UHP lamps (ywh also sells them)

EDMUNDOPTICS.com sells ellipsoidal reflectors that may fit 150W CDM-T Philips lamp if you want to use Metal Halide lamp

Additional optics may be required to expand light cone from ellipsoidal type reflector since beam angle usually not very large

I will be testing with ellipsoidal and short arc uhp lamps in DIY projector soon and will post results (if succesful)

[Kevlar2]

I've been reading this thread for a while, and even though this was a while back, I must throw in my two bits about the reflector shapes. Parabolic is used to create parallel rays from a point source at it's focus. Elliptical is for focusing said source to the ellipse's other focus (like convex lens). Hyperbolic is to spread out the source as if the virtual image was behind the reflector (like concave lens). Spherical is just a variation of elliptical with both focal points together. The shape is geometrically dependent on the principals of conics and is not universally applicable. Any attempt to move the source in or out to achieve a different focal range will result in aberrations and "smear" out the point source. All shapes can be made shallow or deep, in the ellipse or sphere they will just begin to wrap back around, potentially controlling more light. Just like lenses, no one shape is universally optimal.

However, play with an overhead projector focus, and you will see where the focal point for the light source is. It is contained within the circumference of the objective lens, and has nothing to do with the projected image. Ideally it is a small spot to avoid lens aberrations, but if the lens is large you can get away with a less than ideal light source. The reflector aberrations themselves don't affect image quality as long as the LCD is evenly lit and all that light goes through the objective and is very close to the size of the projected image. I hope my opinion is correct, relevant and therefore can be used to settle some disagreements on here. I am no engineer but I work with my hands and have a good feel for geometry.

[velasoraptor]

if you want to project image for about 5-6 feet distance then use some good quality laptop screen as a source no need to disassemble screen just turn ON the laptop as usual and go to display properties or Graphic properties now rotate desktop by 180 degree(flip image upside down) using settings available. Now place a Fresnel Lens in front of screen to get a nice descent projection on wall at distance of 5-6 feet from laptop.