Well, I have heard so many things about fresnels and the size of a TFT, but for now, I want to make it really clear.
Is there a fresnel lens with dimensions of 304.1 x 228.1 mm in order that every pixel of the 15" TFT is displayed on the projection?
Forgive my sucky english, need to practise more. Reading is absolutely no problem, but when it comes to write...
Is there a fresnel lens with dimensions of 304.1 x 228.1 mm in order that every pixel of the 15" TFT is displayed on the projection?
Forgive my sucky english, need to practise more. Reading is absolutely no problem, but when it comes to write...
I did some update on my project. First I changed the 60 degrees bulb. Now I use a 10 degrees bulb instead, the picture gets much brighter and sharper, becaurse it didn´t work in that way I thought. It works as a normal OHP-setup, but this design is much more effective, you don´t lose that much light that you do in a OHP. If you use a single-ended HID-bulb, I think this design is the only you can use if you want all the light from the bulb. I can tell you it´s much brighter than the normal OHP-design other people use. You can use a condenser lens if you want it even brighter. The bulb I use is a "Philips CDM-T 150W" you don´t need more light. So give up your soup-ladle design !
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[RPD]-Killer said:
Yes, there are.
Freshnel Tech #47, FL 18" (457mm), 190 USD
AWI Industries models ((last number is FL) dia 15.75" E10378-200, E10378-225 , E10378-325, E10378-375, E10378-400-05, also the magnifier with 600 mm FL E10382-05
NTKJ Japan Haven't been able to get contact to them, but they have many good size fresnels.
Brainchild also knows some models he used to build his pj which he considered importing (from China I think).
Optimum viewing angle
Just found that for many LCD's the optimum vewing angle is not a straight angle. Instead some datasheets list 6 o'clock or 12 o'clock optimum vieving angles. I'm quite sure my AUO M150XN05 has an optimum viewing angle at 6 o'clock. That means that as a direct view monitor you should look into it at some angle below the midpoint.
M150XN05 lists viewing angles U/D 40/60 which gives a hint to optimum vieving angle being at 6 o'clock.
Just found that for many LCD's the optimum vewing angle is not a straight angle. Instead some datasheets list 6 o'clock or 12 o'clock optimum vieving angles. I'm quite sure my AUO M150XN05 has an optimum viewing angle at 6 o'clock. That means that as a direct view monitor you should look into it at some angle below the midpoint.
M150XN05 lists viewing angles U/D 40/60 which gives a hint to optimum vieving angle being at 6 o'clock.
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Optimum viewing angle (cont.)
So practically this means that the best possible contrast for a LCD panel is not achievable at 90 degrees angle but less, and the LCD should be tilted. However, that is not bad thing as you can watch your DVD anamorphic and let the LCD tilt take care of the vertical shrinking of the picture so there's no need for an anamorphic lense anymore.
Note that tilting the LCD is just an idea I haven't tested yet (will do it later). I hope that I could increase the contrast from about 400:1 to ~600:1 with my LCD using that kind of arrangement.
(btw. the LCD tilt in picture is for an LCD panel with 12 o'clock optimum viewing angle, you got to think it yourself which way you should tilt your panel)
So practically this means that the best possible contrast for a LCD panel is not achievable at 90 degrees angle but less, and the LCD should be tilted. However, that is not bad thing as you can watch your DVD anamorphic and let the LCD tilt take care of the vertical shrinking of the picture so there's no need for an anamorphic lense anymore.
Note that tilting the LCD is just an idea I haven't tested yet (will do it later). I hope that I could increase the contrast from about 400:1 to ~600:1 with my LCD using that kind of arrangement.
(btw. the LCD tilt in picture is for an LCD panel with 12 o'clock optimum viewing angle, you got to think it yourself which way you should tilt your panel)
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Maybe I was too optimistic.
Here at page 2, 2nd graph you will see the viewing angle vs. contrast ratio measurement for M150XN05 panel (from BenQ FP567s). At 0 degrees it's only 300:1 and at ~ 12 degrees towards 6 o'clock it hits it's maximum value of 450:1. I haven't calculated yet how many degrees tilt is needed to shrink anamorphic picture (720x576 PAL DVD) in 16:9 to 4:3, but it may be more than the 12 degrees needed for maximum contrast. It's still possible to adjust the picture in software, another option is to build an anamorphic lens that shrinks the rest of it.
Another interesting note on that document was that on LCD brightness when LCD is in power OFF state vs. when the LCD is on and displays white color. It's surprising that the screen (normal mode) is brighter when the LCD is in power of state. If the controller is properly designed the difference is no more than 10% (still quite a lot).
Original M150XN05 datasheets can be found
here.
Here at page 2, 2nd graph you will see the viewing angle vs. contrast ratio measurement for M150XN05 panel (from BenQ FP567s). At 0 degrees it's only 300:1 and at ~ 12 degrees towards 6 o'clock it hits it's maximum value of 450:1. I haven't calculated yet how many degrees tilt is needed to shrink anamorphic picture (720x576 PAL DVD) in 16:9 to 4:3, but it may be more than the 12 degrees needed for maximum contrast. It's still possible to adjust the picture in software, another option is to build an anamorphic lens that shrinks the rest of it.
Another interesting note on that document was that on LCD brightness when LCD is in power OFF state vs. when the LCD is on and displays white color. It's surprising that the screen (normal mode) is brighter when the LCD is in power of state. If the controller is properly designed the difference is no more than 10% (still quite a lot).
Original M150XN05 datasheets can be found
here.
dracul said:
That may be a problem, though in my theory you don't focus to LCD but to the fresnel on it (or slightly behind). However, if you tilt the LCD 10-15 degrees it's almost the same amount (also the same direction with M150XN05) as you do for the keystone correction with the fresnel.
You can view DVD anamorphic practically with all DVD (software) players (PowerDVD etc.). Some players allow you to choose almost any scaling. Maybe it's worth of getting some real test DVD for tuning or burn own test CD / DVD /DivX CD/VCD CD etc.
mhelin
yeah ive thought in your ideas and still have a few tests to cunduct on the lcd tilting for contrast and brightness, i thought in tilting the lcd forward as then a brighter picure comes out but then the contrast goes and so does the colour, if u tilt it back then the screen goes the opsite way and gets darker and u get more darker contrast, personally i found 0deg the best as in looking strait into it but i think just off set u could be onto somthing here, as i said i havnt fooled with this too much so your da man in this, keep us posted and let us know on your findings,
as for those who dont know the front of a lcd is a vertical polarity and the back is horizontal, manufactures do this on purpoise because the veiwer normally sits right infornt of the screen and not to the side, how ever a lcd will work with the polarity in the oposite direction and some are projuced for certain aplications but the majority are as stated above.
Trev
yeah ive thought in your ideas and still have a few tests to cunduct on the lcd tilting for contrast and brightness, i thought in tilting the lcd forward as then a brighter picure comes out but then the contrast goes and so does the colour, if u tilt it back then the screen goes the opsite way and gets darker and u get more darker contrast, personally i found 0deg the best as in looking strait into it but i think just off set u could be onto somthing here, as i said i havnt fooled with this too much so your da man in this, keep us posted and let us know on your findings,
as for those who dont know the front of a lcd is a vertical polarity and the back is horizontal, manufactures do this on purpoise because the veiwer normally sits right infornt of the screen and not to the side, how ever a lcd will work with the polarity in the oposite direction and some are projuced for certain aplications but the majority are as stated above.
Trev
Has any of you guys thought about using fiber optic? I was watching This Old House Classic and they showed a track lighting device were 250 watt quartzs light bulb transfered light to8 fiber optic cables. The light came out of cable was really bright, this could probably be used with a small lcd, Idon't know if it would transfer the heat from the bulb through the cable or if the cable causes the intensity of the light to decrease. Just thuoght I'll this concept around.
Brand of Ballast
I am looking at building a projector for my brother and was looking at Ballasts. I looked at the diylabs.com and saw that they sell the IceCap ballast. Does the brand of ballast make a difference? The IceCaps are quite expensive yet I have seen others on sell through ebay and other places that are much cheaper.
Thanks!
I am looking at building a projector for my brother and was looking at Ballasts. I looked at the diylabs.com and saw that they sell the IceCap ballast. Does the brand of ballast make a difference? The IceCaps are quite expensive yet I have seen others on sell through ebay and other places that are much cheaper.
Thanks!
I calculated that tilting the LCD 12 degrees needed for optimum CR with BenQ LCD will have little effect to picture height. It will shrink from 228 mm to 223 mm which is practically unvisible. For anamorphic correction (4:3 -> 16:9) you have to tilt the LCD 41.4 degrees which makes the CR to about 10:1 (really really bad). So it won't work but the 12 degrees tilt is recommended with M150XN05 as well as using split fresnel with this LCD. Going to test it tomorrow.
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I can see an improvement in contrast when tilting the panel. Unfortunately I also noticed that my condencer lens was broken and had to take it out (in three pieces), it was propably too close to the bulb and couldn't stand the heat. As a result the image isn't as bright as it was with the condencer.
Possible flaw in "fundamental principles"
Hi!
First... I might be wrong on some aspects but I think this stuff I am going to say is at least worth thinking about...
I've been reading (and also participating sometimes) stuff on this forum for some years. There has been tons of discussions about the stuff that is behind the LCD, the problems and so on. I think that there is on fundamental error in the way the most people think about this stuff. We are wondering about point light sources and so on, but has anyone noticed that with about any kind of a reflector the light source has nothing to do with a "real" point? And how about the few people who have succesfully made projectors with fluorecent lights? What about the fact that you can project ANY bright image with a projection lens? Do you see where I am aiming here?
People... it does not matter if you have a point lightsource... all that matters is that the lcd should be as bright as possible. The method how that is achieved is not so important, the main thing is to have evenly lit as bright LCD as possible, because the brighter the real image that you are projecting is, the brighter will be the fake image on the wall after the projection lens. We are NOT projecting the lamp or anything behind the LCD, we are projecting the LCD, and that is how the optics should be thought also. Think about it... experiment and so on...
Regards
HB
Hi!
First... I might be wrong on some aspects but I think this stuff I am going to say is at least worth thinking about...
I've been reading (and also participating sometimes) stuff on this forum for some years. There has been tons of discussions about the stuff that is behind the LCD, the problems and so on. I think that there is on fundamental error in the way the most people think about this stuff. We are wondering about point light sources and so on, but has anyone noticed that with about any kind of a reflector the light source has nothing to do with a "real" point? And how about the few people who have succesfully made projectors with fluorecent lights? What about the fact that you can project ANY bright image with a projection lens? Do you see where I am aiming here?
People... it does not matter if you have a point lightsource... all that matters is that the lcd should be as bright as possible. The method how that is achieved is not so important, the main thing is to have evenly lit as bright LCD as possible, because the brighter the real image that you are projecting is, the brighter will be the fake image on the wall after the projection lens. We are NOT projecting the lamp or anything behind the LCD, we are projecting the LCD, and that is how the optics should be thought also. Think about it... experiment and so on...
Regards
HB
Just another point to support my view on this "pointsourceohitissohardtogetstuffbeforethelcdtowork"-subject:
My own projector project is based on a commercial projector (made by sony), and there is a glass/"lens" right after the lightsource, a similar glass to those that dentists have on their lighting, you know, those annoyingly bright thingies that they point at your face while drilling. Kind of a wavy glass with small squares... After that the light is hardly anything like a point source light or paraller or anything of that kind.
I think that in many setups on this forum the fresnell before the lcd does just the same thing, distributes the light evenly on the lcd. So, iI think that the whole setup before lcd is a very powerful backlight, nothing else.
Regards
HB
My own projector project is based on a commercial projector (made by sony), and there is a glass/"lens" right after the lightsource, a similar glass to those that dentists have on their lighting, you know, those annoyingly bright thingies that they point at your face while drilling. Kind of a wavy glass with small squares... After that the light is hardly anything like a point source light or paraller or anything of that kind.
I think that in many setups on this forum the fresnell before the lcd does just the same thing, distributes the light evenly on the lcd. So, iI think that the whole setup before lcd is a very powerful backlight, nothing else.
Regards
HB
I'll just keep going...
Do not think the LCD as an optical device, lens or some kind of a multicolored weird filter, as it is not. The LCD is the actual object that we are projecting, it is quite simple, there is a real object (LCD in the case of most here) on another side of the (projecting) lens, and a fake object (the image of the LCD) on the other, what is after or before this setup does not affect in the basic "operation" on this process of projection. If the real object is brighter, so is the fake object on the other side. If you know something about optics you should be understanding what I am saying...
Do not think the LCD as an optical device, lens or some kind of a multicolored weird filter, as it is not. The LCD is the actual object that we are projecting, it is quite simple, there is a real object (LCD in the case of most here) on another side of the (projecting) lens, and a fake object (the image of the LCD) on the other, what is after or before this setup does not affect in the basic "operation" on this process of projection. If the real object is brighter, so is the fake object on the other side. If you know something about optics you should be understanding what I am saying...
Using a point source and fresnel, or parallel light source just means more of the original light is useful, the higher efficiency of the system just means that lower wattage bulbs can be used. I agree it is possible to use flourescents, etc. and still get a good result, but more of the light will be wasted.
Lower efficiency = higher wattage bulb needed = more heat generated.
Steve
Lower efficiency = higher wattage bulb needed = more heat generated.
Steve
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