| woneill |
mycamel,
Your analyses are excellent, and your use of contact processing and the hand shadow as a tool to manipulate and illustrate the concepts involved here is inspired.
Everybody uses metaphors and concepts they are familiar with as tools to explore the unknown. The more diverse the metaphors and concepts that are brought to the fore in these discussions, the more angles on the same issue we will all see.
Sometimes I liken the process of discovery to the tale of the blind men and the elephant: each picking a different feature of the elephant to explore, reported the elephant to be something different. One, feeling the elephant's tail, thought the elephant was like a rope; another, feeling its leg, thought it to be like a tree; another, feeling the elephant's trunk thought it was like a snake; and so on...
The thing that blows me away about what is going on here is that multiple people from all over the world are able to contribute their own little piece to a project that is driven from a pure desire to solve a problem: it is not for money, or fame, or even just to have a working device - many of us already have a working device of one sort or another, but we all still want to solve the problems and achieve something cool.
Forgive me guys for getting heavy, but do you all realise that this is the first period in recorded human history that such an effort - not sponsored or controlled by any university, industry or government - has ever happened?
Normal people from all over the world collaborating and contributing what they can just to taste success...
At this rate, the blind men will all soon be able to share the true understanding of the elephant...
Cool!!!
Bill.
P.S. No, I'm not smoking anything, I'm just tired and shouldn't be posting things so late... ;) |
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| icculus |
ever heard of Linux? I'd love to see that work(or any open source OS) way more than have a big TV.
P.s.--i know it "works" but i'd like to stop giving my money to microsoft altogether--but i agree, it's late and i probably shouldn't post at all |
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| woneill |
Icculus,
Linux is an EXCELLENT OS. I have been playing with it since the early 90s and it is almost ready for prime-time!!! (Don't need to be a UNIX guru to use it anymore...)
The only problem in this context is that for HTPC, there aren't always the latest drivers for the coolest video hardware...
Bill.
Well worth playing with, though!!! |
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| eebasist |
| Yeah, with linux the only real problem lies in driver support. The OS has huge potential and you get away from the BSOD from MicroCrap products. |
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| Axeman |
I've been thinking this for a while, and it might help out those with LCD panel heat problems.
the first part of an LCD panel is a polarizer. This reduces the light level by passing only light of the correct polarization. The rest of the light is absorbed, and converted to heat. If you used polarizing film(available from edmond optics, I think) in the same orientation as the first polarizer in the LCD, but placed it _between_ the light source and the LCD, the light that would not go through the lcd anyway would be absorbed by that polarizer, reducing the heat on the LCD panel. This would be ideal if you could find a high-temperature polarizing material.
Make any sense? |
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| eebasist |
| makes great sense, but what orientation do you have to do? And how much light is lost by the additional polarizer? We already have the efficiency problem, I do like the idea but I dont know enough about polarization to work with it |
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| Axeman |
| From what I've seen using polarizers, the light loss should be minimal. If you take two identical polarizing sheets and put them together, there shouldn't be much difference in terms of light transmission from only having one polarizer. ( however, If you turn one sheet 90 degrees relative to the other one, it should block out most light) So, this is just a way of relocating part of the lcd system to reduce heat on the actual display. The polarizer in the LCD sees ONLY the portion of the light it would let through anyway. THis means that it won't absorb as much light, keeping it and the liquid crystals cooler! It's not getting rid of heat- the first polarizer should get pretty hot, as it is absorbing half of the light. |
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| Axeman |
one more thing:
you would have to experiment rotating the polarizer until you got the maximum output through the LCD... |
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| biteon |
tell me if this makes "us" look stuppid.
i went to the drive in movie theather last night. this is what i saw.
20'x40' (about)screen, 50-75 yards back was the room with the projectors. i went to get a look at the projectors and so some thing intressting. the roll of film is only 2" wide. that means the the light source is only about 1"x2" max. "how the ****** is that ?."
#1 thats alot of screen to cover.
#2 thats a long distance to cover.
#3 the light travels out side where theres dust mist etc.
#4 this drive in is by the ocean( more mist at night)
is it possible that the light bulb for this projector is small like the 2" wide film?.
sorry but that just blows my mind.
p.s. they had a big cooling system. 7' diameter pipes from the ceiling to the projectors. im guessing they might use air conditioning.
:D :D :D :D |
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| eebasist |
I used to work in a theatre way back when.....these things use massive bulbs....the film is only 2 inches wide, but the bulbs are a bit bigger...typically xenon or used to be carbon arc lamps.......we can't and shouldn't even think about these.....they produce a lot of heat and the power supplies required are huge, and the bulbs easily cost 1000$ each.
Nice thought though |
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| biteon |
| so what type of system are you working with eebasist. |
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| eebasist |
| I'm looking for a dead ellipsoidal fixture to throw a 250 or 400 watt MH into and project the light into a proxima dp5100 lcd projector......i have an OHP with a TVT right now |
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| biteon |
i put abunch of pictures and a plan of what im doing on page 19.
take a look tell me if you see any potentchle problems or what you think about it (advise). thanks
:D :D :D :D |
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| eebasist |
Nice setup.....now comes the fun part, seeing if it will work...only comment i really have is the bulb orientation......is the bulb meant for a horizontal burn....if its not it will lead a much shorter life.....Have you determinined the proper spacing between the light, fresnel and lcd....each reflector/bulb combination are different and can cause you to have a good, crappy, or awesome projected image.....Marklar set his up on a table and then arranged the lights to make the best image.
What lens are you using to project the image? |
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| mycamel |
| quote: | Originally posted by biteon
is it possible that the light bulb for this projector is small like the 2" wide film?. |
Have a look at this theater projector. Down at the botom of the page it shows the lamp and reflector used. These run up to 7kw as opposed to our 'tiny' 400w units! |
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| mycamel |
| quote: | Originally posted by eebasist
I'm looking for a dead ellipsoidal fixture to throw a 250 or 400 watt MH into and project the light into a proxima dp5100 lcd projector......i have an OHP with a TVT right now |
I'm trying that route myself. I found a 10" with 1kw bulb on eBay (~$63 including shipping) and should be receiving it soon. What I hope I can do is modify the reflector to accept my 400w MH.
I figure on turning it upwards, running the beam through a sheet of that IR Blocking film, through a fresnel after the LCD and into the optics from my current OHP. Due to the length of the fixture, I may have to lay it down and bounce it off a mirror. We'll see.
I figure the ellipsoidal reflector should already be optimized for a non-point source being that the 1kw bulb filament it normally uses is rather long. All the focal length math should already be done too. Hopefully I'll get lots of useful light out the front of this animal. |
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| biteon |
the bulb is universal(400mh/u). meaning any postion.
the disstance dim. dont realy matter to me cause i got more than enough room in the box to F around. but this is kinda what im planing to do with the lenses and the low-e glass.
low-e glass is going to be set about 1/2" - 1" from the reflector so theres enough room for the air to rotate for cooling reasons.
the first fresnel lenses is placed as close as possible to the low-e glass so it catches most of the light from the reflector and sends the light basically striat forward.
the second fresnel is to consentrate all/most of that light on just the lcd(ill lose some light cause the light coming out of the second fresnel is a circle and the lcd is a rectangle, im going to lose about 1/3 of my light there but it dosent matter to me cause ive allready tryed it and it still worked out pertty good.)
im using a delta IV projection lens i works but the way the lenses are setup the lens has to almost touch the lcd to project a good focus picture there fore meaning the lens has to be bigger than the lcd. un less you modify, but i havent tryed that just yet. i think it will work out with my 5.6" lcd. im going to lunch later.
:D :D :D :D |
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| eebasist |
| Anyone want to imagine the cost per hour of one of those? |
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| biteon |
| what are you talking about |
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| multiplexor |
| quote: | Originally posted by mycamel
Have a look at this theater projector. Down at the botom of the page it shows the lamp and reflector used. These run up to 7kw as opposed to our 'tiny' 400w units! |
is it just me or is the light facing the opposite way to where it should be
what would make this position more efficient? or is it less efficient? |
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| biteon |
dude your tripping that lite in there gets hooked up in two places the front and the back/ kinda like in the halagen flood lights at home depot. one light bulb hooked up to two sockets.
:D :D :D :D |
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| jco9w |
Hey Everybody,
I haven't posted in a while, so I thought I would let everyone know what progress I have made.
I bought a 4 1/2 in Lightolier ellipsoidal downlight on Ebay for $22. It arrived last week. I am planning on going with the Marlakar set up, with the downlight focusing the light, and a lense to disperse it onto my fresnel and LCD.
Today the MH ED28 400 W bulb I ordered from affordable lighting arrived. One problem, it was a BT28 bulb. So Buddy, came through same as he did for Undream, and is sending me out a new one. Cool thing is that I get to keep the other one, so maybe I will buy a socket for it and experiment with it this weekend.
Nice thing about the ED28 is that it will fit right into the downlight with NO need for widening the hole.
So next week I will see how well my downlight collects the light, and try and burn some paper like Marlakar. Then I will start to put it together....
J |
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| prjctr_builder |
i have a DUKANE quantum overhead and a Sharp QA-2500 panel. these are nice products, but something is wrong. after about 5 minutes i start getting this ( if i project BLACk on the screen).
eventhough the transition is smoother, it is very frustrating, it's like all the light is concentrated on the panel. there's nothing wrong with the panel, i checked.
also, i seem to loose A LOT of light. the DUKANE gives off a F*%K ton of light, i can illuminate a city block with it. but when i place a panel on top, it seems like there is a 1W bulb in there.
anyone knows WTF?
tell me plz
aleksey |
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| prjctr_builder |
| there is is.... |
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| xblocker |
Aleksey,
this looks like a bad tooth!
Could be too much heat! Have you removed or replaced any parts of OHP or panel?
Try to blow like hell with a big fan on the panel after start, put it 1" higher, so that air comes also at the bottom side, then watch again! Don't get the panel too high, cause heat is also growing if you move it upwards.
good luck!
xblocker |
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| woneill |
Aleksey,
Sorry to hear of your problems.
How hot is the panel when you get this effect? If you pick the panel up off the projector, does the bottom glass feel hot to the touch?
There should be a fan inside the panel that blows cool air over the LCD. If the fan is working properly, have you checked to make sure the intake for it is not drawing air directly from the OHP output?
If you still have your infocus panel, have you tried swapping it with the Sharp when you get this effect - this might show an issue with the OHP and not the panel (let's eliminate some unknowns...)
Moving on: once everything has reset itself and is operating normally, why not try running the Sharp panel on its own without the projector for a few minutes to see if the issue is due to the panel alone? (Prop the panel up so that you can see some light through it, but it stays cool. Keep the vents open and unblocked. Drive it as if you were using it normally.) It might be a problem with the LCD itself, the Sharp controller board, or the PSU overheating internally.
My old Sharp panel works very nicely, but is VERY critical of temperature, requiring an operating temperature of no more than 40 degrees.
Last, with the panel and OHP warmed up separately, if all seems to be working correctly, place the Sharp panel on the OHP, and check for any immediate signs of problems that could indicate interference.
Good luck,
Bill. |
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| prjctr_builder |
dude, my panel was WAY hotter than 40 degrees when i took it off. it was probably over a 100. i will try to see what i can do..thx 4 the advice.
aleksey |
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| prjctr_builder |
nope, that projector is not nearly as good as the QUANTUM. i have seen the specs, the specs of this thing are way lower than of QUANTUM. and from the picture all i can say is that it is ruined...
aleksey |
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| ap0the0sis |
This might be a good fiund also,
200/250/350 Watt NTP Metal Halide
Illuminator System
Watts 200 DC
Voltage 40.0
Color Temp(K) 6,000
Lumens (LM) 10,600
Arc Gap 1.35 MM
Rated Life (Based on Use) 1,500 - 4,000 hrs
Luminous Efficacy (LM\W) 53
Length 57.0 MM
CRI 90
Chromaticity X = 0.322
Y = 0.335
Lumens Thru 13øApature 6,200
ap0the0sis
P.S. I think those LEDS might actually put some progress on our systems. I sent an email requesting pricing information. |
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| woneill |
Hi Aleksey,
I was talking degrees Centigrade/Celsius - 40C equates to 104F. (100C would boil water...) Sorry for the confusion.
I think it was said before in the last thread: If it felt hot - uncomfortably hot - then it was definitely too hot.
At the point where you would feel uncomfortable, then the LCD will too.
With your setup, you can definitely afford to put that cooling filter in, though - your OHP will definitely have the power to stand the 15% losses from the filter...
Bill. |
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| woneill |
ap0the0sis,
I contacted them about the unit you mentioned, and they didn't appear to like me bcause they quoted a price $1000.
:(
Bill. |
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| ap0the0sis |
HA! What a bunch of F@#$%ers! They actually expect to sell these things? Maybe its because they only sell to distributors...
ap0the0sis
What about them LEDs? |
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| woneill |
The LEDs look similar to a type that was discussed recently here. I think they were called Luxeon Star and represent the cutting edge.
They are very bright, operate at around 5 watts, and output about 25 lumens per watt.
Thus one LED would give 125 lumens(ish).
The 400 Watt MH bulbs give off (I think) around 30,000 lumens.
The LED is rated at 100,000 hours lifespan. A MH bulb gives 20,000 hours easy and costs roughly $30 to $50.
In a couple of years, the LEDs will probably catch up as a practical alternative - just in time to be de-throned by the new Microwave-excited Sulfur balls...
Check out www.luxeon.com for more info.
Bill. |
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| eebasist |
I was talking about the cost of running a 3.5KW theater bulb.
So someone else is trying the same thing as me with an ellipsoidal light.....you are right about them though, the ellipsoidal reflector is designed for a non-point source of light. They ususally expect a fillament that is ~1inch long so we can easily put a 400W MH inside them...the only question that really remains with that is how the F do you cool the bulb.
What lens structure does your ellipsoidal have...ie dist between the lenses, and dist from light source to #1 lens? |
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| eebasist |
| Bill, are you a scientist/engineer? I rarely hear people in the US talk in Centigrade or Kelvin anymore unless they are scien****, or engineers. |
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| multiplexor |
| quote: | Originally posted by eebasist
Bill, are you a scientist/engineer? I rarely hear people in the US talk in Centigrade or Kelvin anymore unless they are scien****, or engineers. |
I dunno, but either way, Bill is very smart ;-) |
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| eebasist |
| Bill is definitly one of the most ingenious folks on the board right now...... I can't wait to see his DP9100 when its finished |
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| woneill |
Hi Guys,
Er, what I am is paranoid... ;)
Actually, I am from the UK which accounts for the centigrade temperature scale, but once upon a time I was both a physicist and an EE until I became disillusioned with the academic establishment in the UK.
Now I work as a computer consultant in NY.
As for ability - I am no better than anybody else here and am still in the process of learning from everybody else. It's the ideas that matter, and the communication of those ideas is what causes progress. There are SO many fantastic ideas shared here. Its unbelievable.
My problem is that I talk more authoratatively than most. I am no more intelligent, though.
Bill. |
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| mycamel |
| quote: | Originally posted by eebasist
how the F do you cool the bulb.
What lens structure does your ellipsoidal have...ie dist between the lenses, and dist from light source to #1 lens? |
I hadn't really thought too much about cooling. I assumed that also would be engineered into the fixture already. I'd further assumed that putting 400w into a fixture engineered for 1000w would allow plenty of thermal 'headroom'.
I haven't received the light yet, and am not sure how to tell the distance to lens 1 from the pictures (or if you CAN!), but the overall length appears to be ~ 3-4 feet. Guess I'll have to just wait to see.
 |
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| eebasist |
| well yes and no it is built into the design of the fixture...... Stage lights get very very very hot. They are made out of thick metal, but they get very hot.......just brushing up against one after its been on will easily burn. I know I'm going to go that route, but need some type of active cooling just havent made it there yet. |
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| Undream |
| one of the reasons why they get so darn hot is that they almost always use Halogen bulbs. |
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| eebasist |
| Yeah, thats a good point that I forgot about. MH is definitly cooler......the problem with ellipsoidals is there is no real air movement around the bulb because of the reflector and lens assembly. |
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| mycamel |
| Someone please correct me if I'm wrong, but a 400W halogen will produce the same heat as a 400W MH. The only difference is light yield. The same power (watts) is consumed and dissipated by both. |
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| eebasist |
| Nope, they wont produce the same amount of heat. They both take 400W of energy, however more of that energy is converted to light than heat with a MH. Its more efficient use of the energy....unless you wanted heat and not light to come from it |
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| woneill |
mycamel,
Power consumed is the same, but how that power is dissipated is not...
Halogens dissipate virtually all the power as heat: thermal "friction" due to the electrons flowing through the filament cause it to get very hot - usually to around 2800K.
That heat is transmitted: through conduction along the support for the filament back into the bulb housing; as convection of air currents; and as radiant "light" energy (em radiation).
The radiant light energy effectively follows the standard black-body response curve which means that most of the light emitted at this temperature falls into the infra-red band. This kind of light interacts with matter to induce thermal vibrations at an atomic/molecular level and hence causes heat. Only some of the radiant light energy exists in the visible band.
This is the origin of "colour temperature", a term which describes the apparent colour of a black body at the given temperature.
MH, MV, Sodium and Fluorescent discharge bulbs all work a diifferent way: the flow of electrons through the gas of the bulb DOES cause some heating, but the dominant effect is that the energy carried by the electrons, accelerated through the applied electric field, gets transferred to the electrons of the gas. The excited electrons of the gas then, triggered by some means or other, "discharge" to a lower energy level, emitting em radiation of a specific frequency, or a combination of frequencies.
This emitted em radiation (light energy) is either usable directly (MH, MV, Sodium), or needs to be passed through some kind of fluorescent material to produce visible light (the mechanism of the fluorescent tubes).
This discharge mechanism is much more efficient at producing light in the visible spectrum than the thermal mechanisms.
Thus, for every watt consumed, there will be more usable visible light, and less "heat".
Incidentally, the different gasses used for the discharge bulbs tend to produce specific emission frequencies: in the fluorescent tubes, the emission is UV; in the MH bulbs, the emission contains a decent balance of red, green and blue components compatible both with or eyes, and with projection technology; MV bulbs produce a set of frequencies that our eyes can use within limits, but are dominated by the green component, and are not compatible with the RGB filters that projectors use; Sodium bulbs produce variations on a theme of yellow...
This is the origin of the Colour Rendering Index (CRI) that people also talk about...
Bill. |
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| Blockhead |
| ok...it's Blockhead time...I have an ovp ordered thet has 400 watt 5,500 lummen hallogen bulb...I'm doing the usual thing of trying out the panel (Nview Spectra C) on the overhead first to get my feet wet. I have a dedicated room for this project and I have it completely dark (No outside light what so ever)...For you experts out there will this sufice or do you forsee issues with hallogen heat? -thanks |
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| eebasist |
| Blockhead, you'll be fine as long as you dont have ambient light to work with. 5000 lumens will suffice on a spectra C. What OHP did you get? You will have some heat, but you could raise the LCD panel a bit for more airflow...but to watch DVD's you'll be fine, now watching a movie marathon will start to heat up the room a bit. |
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| eebasist |
| Bill, now I remember why I'm not a chemist anymore and getting my MBA.........while i love the sciences, I can't just pull physics like that out of my head anymore.....something about quantum mechanics just really makes me want to cry |
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| xblocker |
eebasist,
luckily we don't need quantum mechanics here, i heard a physist say, 'people who understand quantum mechanics, must be crazy!'
xblocker |
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| prjctr_builder |
i know this is not an audio forum, but i just wanna know...
do you guys think that KLIPSCH 5.1 surround sound system is worth buying?
thanks
aleksey |
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| woneill |
Xblocker,
But, surely of all people here, you know quantum physics???
;)
Bill. |
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| multiplexor |
| quote: | Originally posted by woneill
Xblocker,
But, surely of all people here, you know quantum physics???
;)
Bill. |
I plan on building a quantum computer one day...
the harder the formula to process, the faster it will process it...
it will be wicked! |
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| tech head |
Hey multiplexor
If you give it a problem that is hard enough will it process it before you finish giving it the problem? |
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| xblocker |
woneill,
i would like to, but i only know little about Heisenberg, Penrose and some others, although i was a physics student in my former years. Today siences are just a hobby for me, among others. All i know about quantum mechanics is, it has to do with the influence of measure devices to the measurement itself, e.g. during measurements of photons, which can't precisely defined at a location at a given time.
As far as i know....
xblocker |
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| Blockhead |
eebasist,
| quote: | | What OHP did you get? You will have some heat, but you could raise the LCD panel a bit for more airflow |
- The ohp is a Buhl 2963
-what material do you suggest I use to raise the LCD panel and also what ballpark guess would you suggest it be raise (.25 inch .50 inch .75 inch or more?)
Thank you,
Blockhead |
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| xblocker |
Multiplexor,
then soon we can open a thread: 'DIY Quantum Computers'!?
xblocker |
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| woneill |
Xblocker,
I don't think anybody REALLY knows, though many think they do...
Ah, well...
Bill. |
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| eebasist |
| I'm just waiting to see what happens down at Rice univeristy with molecular computing.....that is some cool stuff that will eventually happen |
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| multiplexor |
| quote: | Originally posted by xblocker
Multiplexor,
then soon we can open a thread: 'DIY Quantum Computers'!?
xblocker |
Now THAT would be incredible, if we could all get together and build a quantum computer. |
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| xblocker |
Yep!
I could spend the power supply!
...i suppose we're getting a little offroad now...
xblocker |
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| multiplexor |
| quote: | Originally posted by xblocker
Yep!
I could spend the power supply!
...i suppose we're getting a little offroad now...
xblocker |
true true :) suppose for the person reading every page, this will be more of a relaxing point in the whole projector discussion :)
though discussing quantum mechanics isn't something one can read lightly... |
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| xblocker |
Keyword: Relaxing point!
Was someone, who already has more or less finished his projector, able to lay back on the coach just to enjoy a movie or whatever, without looking on brightness, temperature, contrast, pixels...?
For me it's hard, although i now have 2 working systems!
xblocker |
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| Blockhead |
Guys,
I recall someone posted a remark about using an s-video to vga converter cable to try to rid the macrovision effect...
I have been looking in to this and I have come across a website that is selling several different types of this...I may look into one of these just to see if they help an s-video signal. Any suggestions as to which one I should get? Moreover have you guys seen or heard anything about these?
Well here is the link...http://www.avtoolbox.com/video-to-vga.htm
Thanks...and eebasist do you have any idea of what material to use to rasie my panel? and what do you suggest is ample distance to raise it?
-Blackhead |
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| Timtimes |
Somewhere in the plethora of posts, I have seen it mentioned that there is seldom any need to worry about these panels specifically designed for overhead projector use.
I have an NView Viewframe, which appears to be nearly identical to the Spectra C. It has a couple fans built in already to move air about, but I haven't gotten my overhead projector yet to try it out.
It is about to kill me because the OH projector is ALL I LACK before I can try out this panel in the mode it was intended. I know the panel is good because I hooked it up to my old 486 (with TV Tuner card) and I could see (holding up to light) the image. My wife is a school counselor and goes back to work in a couple weeks. I'm counting on her borrowing a projector for me to 'try out'.....
Enjoy. |
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| mycamel |
| quote: | Originally posted by Blockhead
Any suggestions as to which one I should get? Moreover have you guys seen or heard anything about these? |
I bought one of
these from Amazon.com. It works fine up to 1024x768, and cured my Macrovision woes. Someone in the original thread had mentioned it. Less expensive than the equivalent ones on the page you refrenced too. |
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| Blockhead |
Oh I'm sorry guys I was reviewing some of the post and I glanced back at mine a few posts up and I noticed I put Blackhead instead of Blockhead...Jeez thank God it's Friday!
blOckhead |
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| mycamel |
| quote: | Originally posted by woneill
mycamel,
Power consumed is the same, but how that power is dissipated is not... |
Thanks Bill - Makes sense to me now! So, the total energy leaving both bulbs IS the same, but there's a lot more in the IR band leaving a halogen than MH, and a lot more in the visible spectrum leaving the MH than the halogen.
Thanks! |
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| tahustvedt |
I don't know if this has been mentioned before in this thread but you guys should consider making a little anamorphic lens for the DIY projector and placing the lens before the other lenses in the optical path. This will give an optical anamorphic compression without geometry problems. I hope this relates to the discussion here as I didn't read much of the thread.
The other DIY-projectors I've seen don't have the option to run anamorphic DVDs but with a lens that would be possible. The lens could slide in place for anamorphic material.
Just a quick idea. I'm in the optics forum, working on my anamorphic lens. :)
Tor Arne |
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| eebasist |
| Blockhead, i would say .25 inch....but depending on the quality of the OHP and panel....and within the limits of the focusing mechanism you could go higher....you could really use anything you had on had......wood, plastic....anything laying around to keep it flat...doing this will require you to make something to block out the light that escapes so you dont have it act as ambient light in the room |
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| woneill |
Hi Guys,
Does everybody here know what an anamorphic lens does?
Basically, many widescreen DVDs are encoded with "Anamorphic Widescreen". On a regular tv, this results in a picture identical to a normal widescreen DVD/VHS/Laserdisc: you get black bars at top and bottom of the picture.
However, what the anamorphic encoding does, is expand the image vertically within the 724x480 (US) image, so that the black bars are either reduced or removed. The end result is a very tall image stored using more of the resolution of the DVD.
If you have a normal tv, then your DVD player automatically compresses the image vertically to put the black bars in. But if your DVD player knows you have a widescreen tv/projector, then it does not do this, and leaves the image stretched vertically.
The anamorphic lenses allow you to convert your regular 4:3 panel so that it produces a widescreen image. This could be done by stretching the image horizontally, or compressing it vertically, or both. The end result is that you get to use more, if not all, of the pixels on your screen to contribute to the image.
A DVD disc is designed to accommodate stored images with different aspect ratios:
4:3 (normal)
16:9 (Widescreen)
2.35:1 (Cinemascope - not used)
When you see "Widescreen" on the label, the DVD is stored at 4:3 with the black bars encoded into the video signal. When you see "Anamorphic Widescreen" on the label, the video is encoded at 16:9, and there are only black bands encoded if the aspect ratio is wider than that (e.g. 2.35:1).
I was previously investigating the use of cylindrical lenses to get this effect, but it seems that prisms may be an alternative way to go...
Either way, if it works, it will beat the use of cardboard/sheet metal masks.
Bill. |
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| tahustvedt |
How big (small) would the lens have to be to fit inside a DIY-projector?
The main advantages with a lens is increaseed brightness, less screendoor, higher resolution and reduced LCD-artifacts (scan-lines).
If you use a PC to drive the projector then it would also be possible to make a second lens (or an adjustable one) for 2.35:1 and scale the picture on the PC so that the lens can compress it.
Tor Arne |
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| mycamel |
For anyone like me who wants to find out more about orthogonal parabolic reflectors, have a look at US patent #5,765,934.
(http://patft.uspto.gov/netahtml/search-bool.html)
They even have the curve formula in the description.
I had a thought about creating our own reflectors. If you've ever seen fiberglass tubs or the like being made, they start with a mold which gets the finish coat applied first, then the supporting layers laid and spayed on. Once it sets, it gets pulled off the mold, and the nice smooth finished surface is revealed.
Years ago, I experimented with a cone I'd made based on a parabolic curve to reflect sound from a driver facing upwards out 360 degrees. I made it from plaster using a forming tool I'd made from masonite, sheet metal and tubing. This technique was pretty easy and produced a very smooth and fairly accurate surface.
What my thought was, is if we were to create a mold using a similar tool like the diagram I've attached, then layer strips of foil on it, building the layers up using some sort of heat resistant adhesive, then we could produce virtually any shape reflector for which we could plot a curve. If the adhesive would handle the high heat of what we'd stuff into it afterward, we could just keep laying on more and more foil until reaching the thickness and strength desired.
Epoxy might fare OK being that the foil would form a primary heat shield. Any ideas? |
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| woneill |
tahustvedt,
The majority of the projectors here use a large panel (8" to 10") plus a convergence mechanism to beam the light from it into a cone about 1' high into an objective lens that is anywhere from 2" to 6" in diameter.
The conical beam structure feeding into the objective has some implications for the placement of any anamorphic structure if it goes before the objective.
Have you tried your lenses in this configuration, an is it better to place them before or after the objective lens?
Bill. |
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| tahustvedt |
I haven't tried them in this configuration, but they can be made as big or as small as they need to be. :)
The benefits of placing the anamorphic lens before the optics is that you avoid the geometry-distortion that comes from putting the anamorphic lens after the optics like with a normal projector and lens. At least I think you avoid the geometry distortion. :)
Tor Arne |
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| Mario007 |
| After learning quite a bit from this forum and experimenting with a sharp qa-1500 and a dukane projector I have a question. Although my sharp has composite video in which works well I would like to use it with my computer. It seems as though it has a special plug on it and I got it with just a power supply. If someone would be able to post the pinout of a 26 pin vga connector that many panels use or a place to buy such a cable it would be most helpful to me and many others on this board. Easy way of finding the pinout would be a multimeter checking conductiy from one side of cable to the other. Thanks a lot. |
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| Gunawan W |
xblocker:
you said that you had "a little sceptical to bring a fresnel into the image path. Fresnels are good in lighting path, but in the image path, image can't be better than fresnels quality". Have you ever try it and see the result? If not, then try it, you will surprise with the result, it's very little almost unseen the different with or without fresnel in front of LCD panel!
(it depend on how good your fresnel panel quality).
biteon:
your projector using 2 fresnel panel, to converge the light, how do you place the fresnel?
Is it: lamp-fresnel#1-LCD-fresnel#2-objective lens?
Or: lamp-fresnel#1-fresnel#2-LCD-objective lens?
If your setup is the second one, would you mind trying the first one, just to see the different?
Distance between lamp and fresnel#1 = focal length of fresnel#1 (OHP fresnel fl is about 1 ft), placed fresnel#2 an inch away from the LCD, adjust obj. lens until you get projected image sharp.
woneill:
latest discussion about using diffuse lamp and treat LCD panel as big and even light source.
Is it like using LOA (powerfull fluorecent lamp) that was discussed in part 1?
It failed, because the light spread away and lost.
Maybe using second fresnel after LCD will bring back the light beam and converge to obj. lens.
What do you think?
Thank's. |
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| woneill |
Hi Gunawan,
I think the stuff we have been talking about recently differs from the LOA setup in two ways:
1) The LCD is quite directional, and has poor efficiency for light rays VERY off-axis (by that I mean light rays that diverge considerably from being perpendicular to the LCD). Many LCDS seem to have a noticeable fall-off in intensity once the angle of the light is > 20 degrees from perpendicular. Thus the LOA light sources would be very inefficient due to their absolutely diffuse output.
2) Like the LCD, the fresnel is quite limited in its viewing angle: one of the compromises in the construction of a fresnel that allows it to have an f-stop < 1 is that it is only designed to receive light at a given angle, and transmit that light at another given angle (within a few degrees either way). Most are designed to receive parallel(ish) light and focus it to a point. (See the fresnel-tech website for more info). When they describe a high quality fresnel, they generally specify the position of its "conjugates". These are the points where if a light source is placed at one point, its image can be effectively viewed at the other without distortion or scattering. Thus, most fresnels are designed to have the incident conjugate point at infinity, and the image conjugate point at the lens's focal point. If a viewer is placed at this conjugate point, then the fresnel will operate without significant distortion. The further away the viewer is from this conjugate position, the more distortion that is introduced by the fresnel. The same can be said for the position of the light source - the more its rays diverge from parallel, the more distortion is observed (placing an LCD emitting parallel rays close to the fresnel is in interesting philosophical point...). This is why the fresnel's can be quite directional - using it one way around gives virtually no distortion, and using it the other way ruins the image. This is also the prime reason that most OHPs use two fresnels facing each other...
Where I am trying to get to here, is that the way we are using the fresnel, it is optimised to take a roughly parallel beam coming from the LCD and beam it into a light cone with its apex at the main objective. Slight divergences from parallel in the light from the LCD are within the tollerances of the fresnel, but majorly diffuse light sources are going to give poor results with lots of scattering and distortion.
Thus, unlike the idea of throwing a LOA behind an LCD and putting a lens in front, this requires some more precise engineering. A fresnel might help, but the diffuse nature of the LOA is still far from optimal.
The situation is actually slightly more complex than this, because the optical qualities of the objective need to be fairly closely matched to the fresnel.
The fresnel is operating in magnifier mode - meaning that the light source (LCD) is placed closer then its focal point (the rays from the LCD are never 100% parallel, and hence the philosophical point mentioned earlier is resolved - yup, too much coffee!).
In this situation, even though the rougly parallel light is being beamed from the fresnel into a cone shape, the image produced by the fresnel is actually virtual - behind the fresnel, and behind the LCD itself (this is standard magnifier theory, and the reason reading glasses work - this is not just one of my crazy schemes that would have worked if it wasn't for those meddling kids...).
In order for the objective to correctly focus the image, it must be placed not only at the correct point relative to the virtual image of the LCD to focus the image on the screen, but also close to the conjugate point of the fresnel to actually make the most of the light cone, and avoid any distortion... The two points must be very close, or else, brightness, contrast and clarity suffers.
Before everybody screams, "I told you so," though, it must be said that the optics of an OHP are already optimised to work this way: the fact that a normal transparency is placed on top of the fresnel layer, and not sandwiched between its two fresnels is purely a function of convenience: it is very difficult to write on a transparency when it is between two fresnels... ;)
This is why the focal lengths of the various objective lenses for these devices are different to what would be expected if you were using the standard projector focal length calculations for original image position : projected image position...
Overall, my own personal recommendation for these configurations is to use one or more roughly parallel light sources to illuminate the back of the LCD, place a single fresnel close to the emitting surface of the LCD, and beam the light to the objective. This captures more of the light from the LCD, and relies less on the quality of the original light source being a point emitter.
Having said all that, if the LOA devices are able to produce a very high intensity light, equivalent to the MH bulbs, but without the heat, I believe that there is a fairly easy way to convert their diffuse output into a single high quality point source without TOO much loss. I was never able to find a VERY high brightness bulb at Home Depot (there are no WalMarts near me), so I never explored the option fully.
Bill. |
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| multiplexor |
| quote: | Originally posted by mycamel
It took me a while, but I think I’m beginning to understand why a point source would make it easier to produce sharp images, versus multiple sources or diffused light producing blurry images by thinking of light sources and shadows. Thought I’d share it with the community here.
When we project, we introduce something into the light path to produce a shadow of some sort, color or just varying degrees of gray. That something can be though of as producing a shadow.
On a clear, sunny day, the sun is our point source and darn near parallel because it’s so far away. The shadows we see are sharp and distinct. If you hold your hand over the ground, you see pretty much the same sharp shadow as when you move it closer to the ground.
On a hazy or overcast day, clouds diffuse the light, which is essentially the same as having many sources from many angles. Shadows are now fuzzy even though the source light began from the same point and parallel source. If you hold your hand over the ground, the shadow becomes more distinct as you move it closer to the ground.
If you’ve ever done your own photographic processing, chances are you’re familiar with contact prints. Putting the film directly against a piece of photographic paper, and exposing it to light is how this is done. In this case, we WANT the light to be diffused so there are no parts of the paper lighter or darker than another.
Now, if we put a fresnel lens really close to the output of an LCD panel, what we’re doing is essentially the same as the sun on a hazy day, but holding our hand close to the ground. We’ll get sharp edges on the colored shadows we’re putting onto the fresnel lens. The more parallel the rays are, the sharper the edges of the image will be!
Consider the attached diagram. |
If you used a fresnel between the light sources and the lcd panel, would it still create a "shadow"? I thought from reading here, the light would straighten out once it passes through the fresnel? Or am i deeply mistaken? :) |
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| woneill |
Hi Multiplexor,
The shadow is being caused by the LCD shutter on the surface of the fresnel.
The smaller the shadow, the less of the fresnel that is affecting the image, and hence, the less distortion to the overall picture. Ideally, you would have them flush, except then you get moire banding.
The problem with fresnels is the same as with any big lens - the bigger its surface, the more accurate that surface needs to be so that all light rays emanating from the same physical point get refracted to end up at the same point on the projected image.
With ANY big lens it gets difficult. It also gets difficult to reduce the focal length and maintain the lens size - again, the shorter the focal length, the higher quality the lens surface must be.
This is why most high powered magnifying glasses and lenses are either very small or very expensive.
The fresnel allows a very short focal length with a very wide aperture, but can only do this well if the light emenating from a point only gets refracted by a tiny localised part of the lens surface. In this way, the lens only needs to be made with the surface tolerances of a much smaller lens.
Bill. |
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| woneill |
Additional thoughts...
I would think of any convex lens (fresnel or otherwise) reducing the divergence of the light from a given point, rather than straightening it out.
In magnifier mode (light source closer than the focal point), the lens does not have the power to reduce the divergence so much that the rays re-converge at a new image. Instead, they simply diverge less, creating the impression to a viewer that they are coming from an object further away than the real light source.
In projector mode (light source further than the focal point), the lens is able to converge the diverging rays so that they all meet up at a single point in space. This point is the conjugate image of the original light source, and corresponds to the projected image. This is all focussing is: you move the objective lens until the diverging rays emerging from the LCD surface are re-converged at the screen.
This is one of the reasons a bigger objective increases brightness - more of the diverging light actually goes through the lens and gets refracted (converged) back to the same point on the image.
Regarding my point in an earlier post about parallel rays: they do not need focussing to produce an image. Thus, you could hold an LCD panel above the ground so that the sun shines down through it, and if it is a sunny day and the LCD does not cause too much divergence than you should see the shadows of the LCD shutters on the ground.
The more divergence, the closer you need to be to the ground before the shadows overlap each other and begin to reduce contrast. Too much overlap, and the contrast reduces to zero. Hence, closer is better...
Bill. |
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| xblocker |
Gunawan,
i still haven't tried a 2. fresnel, cause i first had to change the distance between lamp and the 1. fresnel to get a rough parallel beam out. The lamp adjustment of my normal OHP only allow a small range of up and down. I hesitate of modifying it cause i probably will sell it. I've got a brandnew 3 panel projector from ebay which is miles ahead from my OHP setup. 800 ANSI, 120w UHP lamp, SVGA, over 90% illumination uniformity, zoom lens, it's great!
But i'm still interested into the questions discussed here, cause i wanna know, how things work!!
xblocker |
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| biteon |
hey u guys
ive been testing and its not going so well (ill tell you later tonight why)
i made a reflective light tunnel (it helped out ) but directs heat to lcd.
one very important queston i need answered. will the lcd work with out the front polarizer?
i might test that out cause of two reasons. #1 cause my lcd is almost shoot. #2 cause i want a way higher res. lcd.
talk to you later.:D :D :D :D |
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| tech head |
It sounds like you went the way of the tech head.
I still follow the thread and post every now and again but I am enjoying teh projector I bought on ebay.
I'm still working on building one but it has taken back seat to my hovercraft.
Joe |
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| xblocker |
woneill,
for a further clarification, is it that what you mean? Two options here:
1. point light source (forgot spherical reflector)
2. several roughly parallel light sources
The gaps between light sources on #2 could be a problem!
tech head,
i knew the time would come....!
greetings
xblocker |
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| xblocker |
| Sorry, pic doesn't load completely!? |
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| woneill |
Hi Xblocker,
For the first diagram, I would say yes - definitely.
For the second diagram, I would not use the fresnel between the light sources and the LCD because the light beams are already effectively parallel (assuming parabolic reflectors). Producing the parallel beam is what the first fresnel is for in the top diagram.
If the light sources are small, and they have SOME divergence to each beam, they could be arranged close enough together to avoid gaps in the illumination.
Hexagonal packing would maximise light density.
Bill. |
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| xblocker |
Damn, i indeed forgot to remove the 1. fresnel on second drawing! Thanks for hint!
I suppose, most of the people would prefer the single light source setup, less wiring, lamps, ballasts...,and also a large IR-filter would be needed.
xblocker |
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| woneill |
Hi Xblocker,
Definitely, a single MH/Xenon lamp is easier to setup than many of the same.
One of the things I was thinking about, though, is the size of the big 400W beasts that everybody is using. They require a big reflector which has been hard to find and harder to make.
(The recent investigations into replacement stage lighting reflectors might give interesting results: they seem to be selling at $20-$30 for a high power elliptical reflector.)
Multiple (physically) smaller bulbs might also be easier to harness efficiently, and if we can utilise more of their output with better reflectors, we might not need to consume as much power to get a decent output.
Then, there is always the possibility of arranging multiple little MR11/MR16 halogens into a bank. If they were connected in series like Christmas tree bulbs, they could be wired directly across the mains with a fuse and a series diode to give them the DC drive that they need (but only by someone who knows what they are doing...)
They are definitely not as efficient as the MH bulbs, but they can be bought cheaply with a narrow beam (11 degrees) which might actually be more efficient in feeding the screen than some of the big 400W MH variants. They would DEFINITELY need both a UV filter and a very good IR filter, though. But, compared with the 50 hours you get from a single OHP bulb, a bank of these, drawing equivalent power, but lasting 2000 - 3000 hours may be a cool alternative for many people.
They would also allow a much more compact overall projector size - possibly down to a cubic foot.
Bill. |
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| biteon |
my fresnel idea didnt work. but i think its be cause the mirror reflector make it seem as if there is 40 of these lights stacked togetter. kinda like when your in a room with two mirrors, one on op****it sides of the walls, you see 50 etc reflections of your self. so basicly my light wasnt going in a some what forward direction as i plan it and it didnt work. i still think it might work with a different reflector maybe made of sheet metal but i think i got a better idea.
some one i work with said to make a funel. i thought of it be for just like alot of people probbly have but im sure every body think it might be the end of there lcd(i figered thats why every body puts there light about a foot or so away from there lcd). well i did a funnel with sheet metal.there is still some big holes i loose alot of light from, because i threw it all to getter using my setup that ive been working and telling you guys about. well lets just say im getting closer. im planning on making a new reflector/ with a funel/ and a very good cooling system.im gona try my best to get you a picture tonight of the results"the projected movie"but that might not happen cause its midnight in ca right now,and i need to find two AA baterys for my cam. if not tomarrow night i will post a pic.
:D :D :D :D
ps. "i think" the front polvarizer is to send the light forward on a lcd. i might be wrong. so maybe if i take it off then set my delta IV projection lens right on the lcd (my projection lens has to be very close or touching the lcd to project)to do the same job as the polvarizer, sending the light forward,projecting the light, and sence one polvarizer is gone i might be projecting alot more light through the lcd. but i think that might only work with my projection lens or a setup that can catch the light right at the lcd before it gets destorted picture projection. hey its just a theroy i might try it unless otherwise noted. i dont sujjest you guys try to try this im just need some advice. if this dosnt work im probbly out of a lcd for a while.cash has been a problem lately. |
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| biteon |
i think some stage lights might also have glass frenel lenses to spot the light.a stage light is seems to me kinda a good idea .
#1. metal housing already done.
#2. reflector included.
#3. glass fresnel.
#4. maybe just needs some little modifying.
but right now im sticking to what i got.
no picture tonight, maybe tomarrow night. note my projector works out right now for video game and movie (when day seens are playing) due to brighter colors.some night seens in movie dont realy hit spot(alittle dim)
one part of my goal is to see the picture clearly with out having the bightness adjustment up(exsample of brightness over kill,see undreams result picture of his video game projection).no offence cause this **** is really hard long technical project. but im geussing if undream video game projection is bightness over kill,his movie projection is probbly worse.thats what ive notice with my projector.games and cartoons look better than movies projected. so go figger.
:D :D :D :D |
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| mycamel |
| quote: | Originally posted by biteon
i think some stage lights might also have glass frenel lenses to spot the light.a stage light is seems to me kinda a good idea .
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I received the lens for the Strand fresnel light I'd ordered, and can tell you that the fresnel is only good for what it was intended for! The prisims (ridges) are very wide apart, and the backside of the lens has a pebble finish to disperse the light. Great for stage lighting, but not good if you're trying to send the rays in a particular direction like we are. Our good old page magnifiers are more appropriate for that.
The reflector for the fresnel light isn't going to work for me either. The focal point is about 1 inch, but the light source of the 400W MH is farther than that from the outer glass envelope. So you can't get the bulb's light source in close enough to let the reflector do its job properly.
My leko (ellipsoidal with lenses) is supposed to be delivered today. I'll play with it and let everyone know what I find. |
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| Undream |
| what do you mean brightness overkill? Those pics that I posted were with default brightness/contrast settings on the dreamcast and Sharp QA1750 panel, I have never even touched the brightness/contrast controls at all. Maybe I should have, could possibly get a better image. heh. |
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| biteon |
on your web page the "june 9 sucsess pictures"
im looking at the pictures of your projection when the room is pitch black. the up side down picture looks good and sharp other than the fresnel is kinda projecting the light on the lcd unevenly.i had that probblem when using to many frensel lenses and the mirror made it seem as if i had 50 mh bulb stacked togetter. if you look at the two taxi intro projected pictures at the bottom of the page you'll see this
#1. your black isnt pitch black, its kinda faded alittle.
#2. the white letters are so bright that there glarring white light beyond the letters.
brightness over kill
your projection should be easy to fix that problem if its not fixed allready.
i figger that because
#1. on june 9 you werent even using a reflector there fore you still can get way more light passing through which will probbly make your screen look more brightness over kill but still good cause then you can adjust the bightness etc. settings and have enough light to work with.
#2. *****ing around with the fresnel etc. or something to make the light spread evenly on the lcd might be a easy job to.
ive seen your reflector with the cooling sys. and i still think you should change that if you havent already. your fans are taking away very important parts of your reflector and reflection of your light. maybe it better if you set it up so the fans arent in the way of the reflected light and also not attached to your reflector where your have to cut holes in your reflector. might also help making your light more evenly spread out.
to night when i post my picture you guys are gonna see some probblem that im having.for instantance my lcd is a tad bit bigger than my projection lens so the edges fade to black. the two boards i use to keep the lcd polvarizers intact only allows direct light around the perimeter there fore making the edges alittle dimmer. but i cant realy do notting about it unless i get a smaller lcd. when i bought my lcd i didnt know what i know today, or else if i did id get a supper high res and high contrass smaller lcd maybe a 3"-4" to go with my crappy projection lens. also if any one has a delta IV projection lens and has a problem with it cut the corners of the lcd picture there is something you can do to help that just a little bit. if you open the lens setup you will see a paper circle that you can take out to help alittle bit(not much). no i dont no why the paper circle is there but there is probbly is a good reason.
tonight im gona take a picture of a movie (dark seen and a day seen) then a pictue of a video game from the ps1 or if my sister lets, ill use her ps2(it probbly has better graphics).?'s etc.
:D :D :D :D |
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| ap0the0sis |
Is $30.00 to much to pay for a piece of first surface mirror that is 8" X 10" ?
Please advise
ap0the0sis :D |
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| biteon |
draw me out a cut section of your lcd. i just want to see how its set in the plastic housing(chassy).conferm front to back.thanks.and ill show you the problem with my lcd with the two board fix i did.i think but not sure but we might have simular problems in that area(with the lcd housings dimming light at the perimeter of the lcd).
:D :D :D :D |
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| biteon |
| regular mirrors are cheap if you buy the 12"x12" tile size mirror package. but im not quite sure what a first surface mirror is. |
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