Some thinking,
Why commercial lcd projector can use small lamp with
not so high lumen and produce bright image?
Because they use very small LCD panel (1") and the lamp
highly focused on LCD, no light spread / bounce around.
They need only XX lumens/inch.
If we use larger LCD panel (let say 14"), we should light it up with 14x14=196 times XX lumens to get the same output!
Am I right??????
Why commercial lcd projector can use small lamp with
not so high lumen and produce bright image?
Because they use very small LCD panel (1") and the lamp
highly focused on LCD, no light spread / bounce around.
They need only XX lumens/inch.
If we use larger LCD panel (let say 14"), we should light it up with 14x14=196 times XX lumens to get the same output!
Am I right??????
Screens
Be careful when trying to calculate lumens. Much of it involves human perception of light intensity.
I agree that the small sized screen, if condensed, will be brighter, because of the sweetspot in the dispersed light.
When using large LCDs, I think it would help if the light is guided to the LCD.
On another topic...
I haven't talked about this before, but the screen type is very important too.
For example, let's use the screen rating of 1 to 3, in .5 increments.
A .5 grain screen is not as reflective as a 2.5 grain screen. However, as the figure rises, the angle of reflection lowers. That means that off axis viewing suffers. If you are using a white wall as the screen, it might not be as reflective. And who's to say the white wall is the correct white color, or colour?
Has anyone used a projection screen for testing?
Vince
Be careful when trying to calculate lumens. Much of it involves human perception of light intensity.
I agree that the small sized screen, if condensed, will be brighter, because of the sweetspot in the dispersed light.
When using large LCDs, I think it would help if the light is guided to the LCD.
On another topic...
I haven't talked about this before, but the screen type is very important too.
For example, let's use the screen rating of 1 to 3, in .5 increments.
A .5 grain screen is not as reflective as a 2.5 grain screen. However, as the figure rises, the angle of reflection lowers. That means that off axis viewing suffers. If you are using a white wall as the screen, it might not be as reflective. And who's to say the white wall is the correct white color, or colour?
Has anyone used a projection screen for testing?
Vince
lost of light
With reflector, light can beamed with degrees of beam- spread we want. Ajust lamp distance to LCD panel until lCD panel will fit inside the light beam.
Now, the problem is (see drawing below):
lamp with reflector
. . |
. . v -------H----------->
. ./ . . . . . H .\ . lost of light
./ . . . . . . H . .\
(O . . . . . .H x . () <-- lens
.\ . . . . . . H . . /
. .\ . . . . . H . / . lost of light
. . . -------H----------->
. . . . . . . H=LCD panel
x= useful light beam
ignore the dotted!
If we use LCD panel bigger than the lens, you see, we lost lots of light, only small light beam goes directly to the lens (x area).
Using condenser lens before LCD panel to concentrate light might help, but the lens size must be bigger than LCD. Fresnel sheet, it's easy to find and quite big size, but the focal length (f) is too long. Why?
Because the lamp must put at more than 2f distance from fresnel sheet, to produce concentrate light.
That's why we need more powerful light source to compensate lost of light beam.
My thinking is, using more than one lamp and condenser lens so each lamp can cover partial area of LCD panel and all together beamed to the projector lens.
Any better idea?
If we can find cheap 3" LCD panel with SVGA resolution, it'll solve our problem, anyway, anybody knows, where to find 10" or smaller LCD panel, TFT, SVGA resolution, VGA or component input?
Merry X'mas and Happy New Year to you all.
See you next year!
With reflector, light can beamed with degrees of beam- spread we want. Ajust lamp distance to LCD panel until lCD panel will fit inside the light beam.
Now, the problem is (see drawing below):
lamp with reflector
. . |
. . v -------H----------->
. ./ . . . . . H .\ . lost of light
./ . . . . . . H . .\
(O . . . . . .H x . () <-- lens
.\ . . . . . . H . . /
. .\ . . . . . H . / . lost of light
. . . -------H----------->
. . . . . . . H=LCD panel
x= useful light beam
ignore the dotted!
If we use LCD panel bigger than the lens, you see, we lost lots of light, only small light beam goes directly to the lens (x area).
Using condenser lens before LCD panel to concentrate light might help, but the lens size must be bigger than LCD. Fresnel sheet, it's easy to find and quite big size, but the focal length (f) is too long. Why?
Because the lamp must put at more than 2f distance from fresnel sheet, to produce concentrate light.
That's why we need more powerful light source to compensate lost of light beam.
My thinking is, using more than one lamp and condenser lens so each lamp can cover partial area of LCD panel and all together beamed to the projector lens.
Any better idea?
If we can find cheap 3" LCD panel with SVGA resolution, it'll solve our problem, anyway, anybody knows, where to find 10" or smaller LCD panel, TFT, SVGA resolution, VGA or component input?
Merry X'mas and Happy New Year to you all.
See you next year!
Hello gunawan,
the light beam of the light source must be imaged into the projection lens. That means, the condensor lens is an optical subsystem, which is a projection itself. The distance between lightsource and condensor should be >f and <2xf. Condensor must be > LCD.
The focuslenght of projectionlens depends of the size of lcd-panel. If focuslenght is smaller than diagonal of lcd-panel there will be optical distortion because of the physics of optical lenses.
xblocker
the light beam of the light source must be imaged into the projection lens. That means, the condensor lens is an optical subsystem, which is a projection itself. The distance between lightsource and condensor should be >f and <2xf. Condensor must be > LCD.
The focuslenght of projectionlens depends of the size of lcd-panel. If focuslenght is smaller than diagonal of lcd-panel there will be optical distortion because of the physics of optical lenses.
xblocker
Hey guys, I just found this forum the other day and have read from begining to end. I've been working on a projectior for some time now with recent success. Here is what I have so far. For the ouput lens I have a Delta IV lens from a rear projection tv I stripped for parts, still have the 40" screen for another project. The LCD is a 5" model from Parts-Express which cost around $120. The hardest part of the project was creating a lightsource that would work without a hotspot. The first test was a 50w hologen. It didn't work that great, was like watching through a peephole with the hotspot. I tried several methods of correcting this, but nothing that was acceptable. The second light source I tried was a 300w hologen I ripped from a tourch light. It worked ok, but it still wasn't what I expected and there was the heat issue. The third light source I tried was a 65w flurex light from Wal-Mart ($25) that is equiv. to a 500w hologen and is supposed to produce 8,255 lumen. This worked very well, it was pleanty bright and produced very little heat. I have a 6.5 foot screen to test with and the results so far are acceptable. I have had bad luck since. The ribbon cable on the LCD broke from moving it around testing. I'm going to have to purchase another. I would like to see if anyone else has tried a Fluorex light source and if so, results?
Hello.
I found this thread (what ever that is/means) few days ago and read it through. Few months ago I tried to build this "monitor ohp" where I have the OHP lightbox thing replaced with PC-monitor which I thought was my very cool **** thing invention(apparently I'm not the only one who thought that up) but as we no it doesn't quite work. Too dim. Cool otherwise though, I could get quite sharp picture actually (but very dim ). Somebody asked about testing to a projection.. ****, I forgot the word. Well I tried anyway the "white thing" which is normally used when projecting something (what ever it is in english, from our language to english it's: whitefabric, so eat that. Anyway the difference was NOT big. Very slight, as well I got and tried an piece of "highpower" fabric I believe it was or something like that anyway, it's expencive, and quite useless, it's brighter (since it's reflection power is better than normal) but you have to look at it from next to your projector it to work properly.
Anyway. I'm not too much intrested to build anything myself, I mainly just want big screen, with low cost. So yesterday I bought an LCD-projection screen to use with OHP. The shopman told me that I need quite powerful OHP. He would sell one with $500. I don't have one right no at all. So now I was thinking if I can build an OHP myself. Just the lightbox thing. I actually still have the OHP mirror/lense thing from my earlier project. But what would be a good light source then, I tried normal 40w 230V "glow lamp" under the LCD and it was totally useless. I could barely see the picture in the LCD-screen itself. The big problem is probably going to be the heat. I thought I would just try like 3 100W 230V lamps or something or some very powerful one lamp (if I figure out where to get one), put it in to a box which has some kind of air conditioning and some kind of glass in top of it (btw what kind of glass or what ever it is in OHP?) but our house is probably going to burn off.
Just before this mail there was someone telling about his project and his good light source but due to my bad english I didn't understand what kind of light he was talking about. Does it release lots of heat? I read halogen lamps generate very much heat. But would this "combining glow lamps(i don't know again what it is in english, but anyway normal lamp in roofs and allkind of home lamps and ****) work? I was today supposed to do some tests if the light power actually increases when I put on another 40w (well actually this one was 60w) lamp next to the one I already have but it burned so there was my test. After christmas I'm going to go to do some lamp shopping, I just don't know if it's better in the end pay the $500 from real OHP than burning our home...
Anyway, I'm just talking **** here, purging my heart.. Thanks for listening. And merry christmas!
I found this thread (what ever that is/means) few days ago and read it through. Few months ago I tried to build this "monitor ohp" where I have the OHP lightbox thing replaced with PC-monitor which I thought was my very cool **** thing invention(apparently I'm not the only one who thought that up) but as we no it doesn't quite work. Too dim. Cool otherwise though, I could get quite sharp picture actually (but very dim
). Somebody asked about testing to a projection.. ****, I forgot the word. Well I tried anyway the "white thing" which is normally used when projecting something (what ever it is in english, from our language to english it's: whitefabric, so eat that. Anyway the difference was NOT big. Very slight, as well I got and tried an piece of "highpower" fabric I believe it was or something like that anyway, it's expencive, and quite useless, it's brighter (since it's reflection power is better than normal) but you have to look at it from next to your projector it to work properly. Anyway. I'm not too much intrested to build anything myself, I mainly just want big screen, with low cost. So yesterday I bought an LCD-projection screen to use with OHP. The shopman told me that I need quite powerful OHP. He would sell one with $500. I don't have one right no at all. So now I was thinking if I can build an OHP myself. Just the lightbox thing. I actually still have the OHP mirror/lense thing from my earlier project. But what would be a good light source then, I tried normal 40w 230V "glow lamp" under the LCD and it was totally useless. I could barely see the picture in the LCD-screen itself. The big problem is probably going to be the heat. I thought I would just try like 3 100W 230V lamps or something or some very powerful one lamp (if I figure out where to get one), put it in to a box which has some kind of air conditioning and some kind of glass in top of it (btw what kind of glass or what ever it is in OHP?) but our house is probably going to burn off.
Just before this mail there was someone telling about his project and his good light source but due to my bad english I didn't understand what kind of light he was talking about. Does it release lots of heat? I read halogen lamps generate very much heat. But would this "combining glow lamps(i don't know again what it is in english, but anyway normal lamp in roofs and allkind of home lamps and ****) work? I was today supposed to do some tests if the light power actually increases when I put on another 40w (well actually this one was 60w) lamp next to the one I already have but it burned so there was my test. After christmas I'm going to go to do some lamp shopping, I just don't know if it's better in the end pay the $500 from real OHP than burning our home...
Anyway, I'm just talking **** here, purging my heart.. Thanks for listening. And merry christmas!
Bitch
He is a link to the mfg website of the light I was refering to.
http://www.lightsofamerica.com/
Look for "Fluorescent Worklights" in the products section.
It may work for your project using this type of light and a fresnel lens between it and your LCD. < Just a thought >
He is a link to the mfg website of the light I was refering to.
http://www.lightsofamerica.com/
Look for "Fluorescent Worklights" in the products section.
It may work for your project using this type of light and a fresnel lens between it and your LCD. < Just a thought >
company who makes small lcd screens and drivers...
cheers guys, after stumbling on this topic a day or to ago it has been a very interesting read...
anyway i found a taiwanese company who make / sell small TFT LCD screens....
smallest screen they sell is 4" (but u can get a tv tuner for it) and its quite cheap....
FYI: http://www.redant.com.tw/main.htm
i know http://www.lik-sang.com sell their stuff...
maybe this will help on the quest, as far as i can see the smaller the lcd the better ...
siy.
cheers guys, after stumbling on this topic a day or to ago it has been a very interesting read...
anyway i found a taiwanese company who make / sell small TFT LCD screens....
smallest screen they sell is 4" (but u can get a tv tuner for it) and its quite cheap....
FYI: http://www.redant.com.tw/main.htm
i know http://www.lik-sang.com sell their stuff...
maybe this will help on the quest, as far as i can see the smaller the lcd the better ...
siy.
Light Source
The light is actually a work light on a small stand. I stripped the stand from the light and used the housing. It has a transparrent cover over the lamp which I am going to attach a fresnel lens to.
The link below is the mfg. Look under products/Fluorescent Worklights
http://www.lightsofamerica.com/
Sorry I didn't take any pics of the results before I wasted the LCD.
The ribbon cable from the LCD to the driver board tore. Not sure if I can fix it, may have to purchase another.
I'll try to post some pics of what I have so far. This may give a better idea of what I'm talking about.
The LCD I'm using is just a standard 5" with NTSC video in. All I need is something to watch movies and such. I don't really need to project PC video as of now.
The last test I completed worked pretty well. The image was viewable with ambient light. In total dark The image was very acceptable and clear. The screen door effect was noticeable up close, but I wasn't able to get far enough away to see if distance would make a difference. There were some minor alignment problems with the original box, so I built another and was moving everyting over when I tore the ribbon cable from too much movement. Next time I will build a permanent mount for the LCD and go from there.
The light is actually a work light on a small stand. I stripped the stand from the light and used the housing. It has a transparrent cover over the lamp which I am going to attach a fresnel lens to.
The link below is the mfg. Look under products/Fluorescent Worklights
http://www.lightsofamerica.com/
Sorry I didn't take any pics of the results before I wasted the LCD.
The ribbon cable from the LCD to the driver board tore. Not sure if I can fix it, may have to purchase another.
I'll try to post some pics of what I have so far. This may give a better idea of what I'm talking about.
The LCD I'm using is just a standard 5" with NTSC video in. All I need is something to watch movies and such. I don't really need to project PC video as of now.
The last test I completed worked pretty well. The image was viewable with ambient light. In total dark The image was very acceptable and clear. The screen door effect was noticeable up close, but I wasn't able to get far enough away to see if distance would make a difference. There were some minor alignment problems with the original box, so I built another and was moving everyting over when I tore the ribbon cable from too much movement. Next time I will build a permanent mount for the LCD and go from there.
Lens
Yea, I almost bid on those same lenses. They are a Delta II where mine is a Delta IV. I'm not sure what the optical difference is but they should work since they are made for a 5" CRT projector anyway.
I'm working on a new mount for the LCD assembly. So I don't destroy the next one. I'm using the old one as a template and will be replacing it with the exact same model. The old one should also work to test alignment and light output somewhat.
Yea, I almost bid on those same lenses. They are a Delta II where mine is a Delta IV. I'm not sure what the optical difference is but they should work since they are made for a 5" CRT projector anyway.
I'm working on a new mount for the LCD assembly. So I don't destroy the next one. I'm using the old one as a template and will be replacing it with the exact same model. The old one should also work to test alignment and light output somewhat.
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