You could replace the backlight in monitor with a mirror and single fresnel (think why single). Then you need a pj lens and a lamp. These are installed to distance of fresnel FL from the monitor so that the lamp (needs also reflector and condencer lens) and pj lens are side by side but so that all light from lamp goes to LCD through it and fresnel to mirror (at which point the ligh rays are parallel), back to the fresnel which condences the light rays to pj lens. This kind of DIY pj is just size of the monitor (can be used in it's original housing) + pj lens + lamp assembly. Should be easier to build also. Latest Dscaler can also mirror the picture vertically so no extra mirrors are needed. Anyone liked to make a proto?
Besides it doesn't matter if the flat cable can be extended or not.
Just cut the mirror and the fresnel to right size (size of the backligh module). You can also get two single fresnels from one OHP fresnel.
Besides it doesn't matter if the flat cable can be extended or not.
Just cut the mirror and the fresnel to right size (size of the backligh module). You can also get two single fresnels from one OHP fresnel.
I don't think so, it's actually quite easy to take apart a monitor and put it back. I could do it in half an hour, but I couldn't build a pj in that time.
Btw, I think reflective pj isn't a good idea as you'll loose so much light when you got to go two times throrugh the panel. I haven't even considered yet if it even works because of the polarization of the LCD panel.
Also why it seems to be a common opinion that portable OHP's (which work like this, though without the LCD panel) don't work with panels???
Btw, I think reflective pj isn't a good idea as you'll loose so much light when you got to go two times throrugh the panel. I haven't even considered yet if it even works because of the polarization of the LCD panel.
Also why it seems to be a common opinion that portable OHP's (which work like this, though without the LCD panel) don't work with panels???
I disagree Mc I have tried this with a gameboy advance a small mirror and a wallet sized fresnel lense and work great, the thing that might be hard to do is find a bright light source for 14" to 15" LCD. I used 250W slide projector removed the projection lense and the condenser lense to focus the light on the screen and it work great.
You got to remember angle of entry is equal to angle of exit.
In this diagram most of the light is just going to shoot straight up not towards the pj lens. You would need to tilt the mirror downwards the same angle as the axis of your light source. So now you need more room cleareance behind the lcd.
In this diagram most of the light is just going to shoot straight up not towards the pj lens. You would need to tilt the mirror downwards the same angle as the axis of your light source. So now you need more room cleareance behind the lcd.
Improved design
Ok, after having my pj (not reflective but usual kind of) working properly I must correct this plan based to use of reflective type LCD's. It's not difficult but makes sense: swap the LCD and the fresnel. When the light comes from the point source it first has to go through the fresnel. Then when it's collimated the light rays go straight through the LCD to the mirror, then back to the LCD and fresnel which then condences the light to the pj lens. So you have to put only the mirror into the LCD monitor (replace the backlight assembly with a mirror). You can use a reflective type LCD as well. Then you need just a single fresnell with grooves down on top of the LCD. Put the light source and the pj len as close as possible to the each other.
To test this you could use a reflective type LCD (Gameboy etc.), a pj lens with ~300 mm FL (diylabs triplet), a page magnifier (like the 100" TV stuff if you've got them), 12 V / ~100W Xenon and a PSU (12V /150W for halogen lamps, a car headlight bulp + psu will cost about 30 EUR/$ or less).
Ok, after having my pj (not reflective but usual kind of) working properly I must correct this plan based to use of reflective type LCD's. It's not difficult but makes sense: swap the LCD and the fresnel. When the light comes from the point source it first has to go through the fresnel. Then when it's collimated the light rays go straight through the LCD to the mirror, then back to the LCD and fresnel which then condences the light to the pj lens. So you have to put only the mirror into the LCD monitor (replace the backlight assembly with a mirror). You can use a reflective type LCD as well. Then you need just a single fresnell with grooves down on top of the LCD. Put the light source and the pj len as close as possible to the each other.
To test this you could use a reflective type LCD (Gameboy etc.), a pj lens with ~300 mm FL (diylabs triplet), a page magnifier (like the 100" TV stuff if you've got them), 12 V / ~100W Xenon and a PSU (12V /150W for halogen lamps, a car headlight bulp + psu will cost about 30 EUR/$ or less).
I thought the 100 inch stuff fresnels spread light out where as the fresnels we use condense the light to a smaller point such as the back of a projection lens?
You realize the light gets cut everytime it passes through an element. So the LCD cuts 50% going from 2000 lumens to 1000 once. Bounced back off the mirror it goes from 1000 to 500 going through the lcd a second time. And then you have the Fresnel. Not sure how much a fresnel cuts but this will also be cutting light as 2 fresnels would.
Cinematographers place filters on a mirror to bounce light but they all know a filter(lcd in this case) on a mirror is a double whammy.
How about this? The catch is you will need twice as much light as with a regular diy projector. My idea below is also to replace the backlight with the mirror. The only reason I would do this is if really felt I could not extend the lcd cables or cable needed successfully. But the huge light loss is the breaker for me.
Attachments
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.