hey everyone,

I'm new. i bought the plans, and i need help...

So i stripped a proview 15.4" widescreen LCD, and have a 3M OHP.

As seen in the picture.....attached...

The problem is that it seems there is some paint or film on the LCD such that it blocks a lot of light.

As you can see from the picutre, the LCD IS NOT letting much light through, hence the picutre on the wall from the screen is extremely faded and dark.

ANY suggetsions anyone? Anybody have experience with this proview screen?

I was thinking the problem is with the OHP not being powerful enough, but I have no clue!!!
Also I didn't do anything else to the LCD. Putting the backlight behind the LCD< the LCD looks just like any other LCD and works fine

Try containing all the light leaks around the LCD. Turn off the lights in the room. This will improve you projected image... then perhaps you can see enough of the image to start making adjustments.

edit: Oh yea, the dark film on the LCD is most likely the polarizing filters that are intregal to the operation of the LCD. Don't remove them as this will destroy your LCD. I don't remember where I read it, but I believe that LCD's only pass about 20% of the light, if that, some estimate it to be around 15% or lower. (someone correct me here if i'm wrong about the numbers)

I cannot see an image on the lcd that is on the OHP. When you look directly at the lcd when it is on the OHP do you see an image at all?

it doesnt look like your monitor is on or you have a signal? otherwise you would atleast see something on the overhead. check your connectors and make sure it is on. may sound stupid but it happens.

the lcd will pass 9% light or less. this is from lcd techonoly assumtions, considering 2 polarizer loses, color layer losses and the blocked light consideration (black space between each sub pixel).

The LCD was on, if you look closely you will be able to see the image.

Turning off the lights and to box it in is completely useless. The light we have now is not nearly bright enough be comparable to a real projector.

So everyone willl have these problems when using an LCD? Do I need a brighter light source?

I was under the assumption that it was *possible* to make a DIY projector with a standard commercial LCD panel (stripped of course) and a standard commercial Overhead Projector (with air control between LCD and OHP surface).

Any opinions?

Scrap the overhead projector parts and start gathering parts to build an LL video projector. If you read the plogs and look at the projections that are achievable I am sure you will agree.

Yes, I do believe it is *possible* to have a decent picture, but you must contain all the stray light, and turn the lights off in the room. There is no way to get a good projection on a wall with so much light... unless you get a really expensive screen, or go with a commercial unit. Do you know what wattage bulb is used in the overhead projector ?

I believe that you will have much more success following the LL design... others have also used OHP parts in a LL style enclosure with very good results.

actually, no, it is not possible.....if you completely box in the area between the lcd and the overhead lens (a must) you **may** get a picture that is watchable, but it will be no where near the same ballpark as a LL design. There are literally hundreds of posts here about this very issue, and infact i think there is a sticky about it.

OHP is a gimmick sold on other websites and ebay.

what about that TomsHardware Central article (both of them)?

I am essentially doing the same thihng, except my LCD choice is the 15.4" widescreen Proview.

I want to build this projector with the lowest possible cost, and the simplest design/construction (i.e. just putting comercial parts together)

you are discussing the brightness here, are you?

well, there was a standard to meassure the brightness on a projector; ANSI lumens. Is as easy as meassurng and comparing.

i'm not sure why you are saying any of this ?? the principals are exacly the same between and OHP and LL design... Light Engine, Collimating/Collector Fresnel (unsplit configuration), LCD, mirror (for turning light path 90°), and projection lens. IMO, the LL design is better in terms of cooling, keystone correction, overall structural integrity, and astetics, plus some other things i'm sure I left off, but there is no reason that the OHP design won't work.

OHP is not the same as the 100" TV gimik you see on ebay, those are two entirely different things. That gimik uses a TV (or computer monitor) and a fresnel lens as a projection lens to project an image... that is a gimik and does not work at all.

cheers,
gs

I know what the 100"TV gimmick stuff is.

What I want is a very SIMPLE projector that I can build with very simple off the shelf parts (OHP, LCD screen, fan) that i just dissassemble and reassemble in the "toms hardware central DIY projector article" fashion.

I have an Infocus X1, but the main reason for building my own projector is because of:
1) I want higher resolution than 800x600. With the proview, I get 1280x864.
2) Higher brightness. I want to be able to use my new projector with some ambient light rather than nearly NONE.

I don't have much access to machine shop tools (drills, saws, wood, etc.) so I would like to not have to machine anything (as much as possible!)

THE PROBLEM I AM HAVING RIGHT NOW IS THAT I AM NOT GETTING ENOUGH BRIGHTNESS. - As you can see from the picture is that the LCD is blocking A LOT of the OHP light....as seen from the above replies, I am told that this is inherent in LCD's. Is there any way around this besides using a more powerful light source (more lumens)?

Now that is clarified, I am using an old halogen 3M OHP (as seen in the image).

I was thinking of using a Metal Hylide OHP, will that boost my brightness by a lot?

I do not have experience with LL, so I don't know how much brighter the LL will be compared to a commercial OHP (Halogen or Metal Hylide?!?).

Note that with a OHP, I don't have to design / build any of my optics, as teh casing and optics are already done - hence a simple, quick, solution.

Thanks everyone for your replies thus far

no offence to you personally

your ohp LOOKS LIKE CRAP!!!!!!!!!!..... have u ever seen a lumenlab projector without the lcd in (everything else in place) .....IT BLOWS YOURS EYES OUT!!!!! its about 50X brighter than your ohp is giving with no lcd (see the left and top of the picture u posted) ......conclusion: Build a lumenlab enclosure.....u also have some major hot spotting there on the ohp

From what I can tell, there are two possible scenarios, depending on the OHP design (I'm not sure which is correct, but I'll give both).

1) The bulb is at the fresnel focus. So the light coming out of the top side of the fresnel is approximately collimated. So, if you look at it from overhead, the lens is only getting a small circle of the total light emitted. Add that to the natural LCD blockage, and you've got a small amount of light.

2) The bulb pushes quasi-collimated light through the fresnel, which then focuses the light down to the lens at the top. In this case, you're shooting mostly non-collimated light through your LCD. The polarization filter will then block almost all your light.

Either could be the OHP design, and neither can be corrected. You're just going to have a really dim image. OHPs work well for paper because it doesn't block non-collimated light. LCDs do so that you don't get funky color blurring. I don't think there's much you can do about it really.

I have seen pictures of this working ok though, so maybe some LCDs aren't as severe about polarized light filtering as others, I don't know. Just don't expect miracles from it either way.

WuLab,

My reply about the 100" TV was directed towards jcrack_corn as he appears to be confusing the two.

I'm not sure that just using a MH (Metal Halide) OHP is going to give you more brightness, it will depend on the lumens that is being delivered. MH will give you more lumens/watt so for the same wattage bulbs, MH will be brighter.

Personally i've never tried the OHP, however for some of those who have, they reported that the OHP tends to be brighter than the LL design. I believe this is a result of the OHP design using a small bulb and an ellipical reflector, which results in harnessing more light and directing it towards the LCD.

Unforunately you must consider some of the shortcomings of the LL and OHP designs. You will get a higher resolution using an LCD panel from a monitor, which is one of the LL/OHP's strengths... however, commercial units do much better in ambient light situations compared to LL and OHP designs. I'm not suggesting you won't be able to make a LL or OHP that you're happy with, but based on what you have said, if you are unhappy with the brightness of the X1 with the lighting you have, you will be even less happy with the LL or OHP design with the same amount of ambient light. If the increased resolution makes up for the lack of brightness, then perhaps you will be happy after all ?

Couple of comments about ambient light.
1) If you can control the lighting, and be sure that any lights that are on do not have a direct path towards the screen, this should improve the projected image.

2) There is screen technology out there (black screens) that are designed for improving the projection in area's with a high amount of ambient light. Although the results are remarkable, so is the price tag... plan on spending thousands of dollars for a 6x8' screen !

Finally, there is no way that I know of to make the LCD pass more light. As Rox has stated, the LCD will pass 9% or less, these are just the limitations of LCD technology and we have to live with them.

Good Luck,
gs

I double what GadgetSmith said.

OHPs have worked. We even have some good pictures in the gallery. However, if you want to watch it with lots of ambient light you will have to take a whole systems approach. And even then, you will have to live with the fact that the contrast will still not be as good as when you watch it in the dark.

Some tips for watching your Infocus or OHP or any projector with lots of ambient lighting.

1. No light can shine directly on the screen. It will kill all blacks. The colors will still show, though. This is an absolute must follow rule.

2. Use a screen that is recessed in a dull black border. The deeper the recess, the less reflected ambient light that will reach the screen. The black border will also help increase percieved contrast.

3. If possible, keep ceiling, walls and floor as dark as possible. This will reduce the amount of reflected ambient light to the screen. Theoretically, if your lights do not shine directly on the screen and you can minimize the reflected light to the screen then you should get a pretty good image with the infocus.

Also, if you plan on making and taking the OHP apart many times then you are playing with fire. Those leads to the lcd panel are very fragile. It would only be a matter of time before you accidentally destroyed them and render the lcd panel useless.

If you plan on only watching movies and don't have money to build a good projector then I would suggest putting the lcd panel back in its original form and using the infocus. If you want to watch TV or play games on a large screen and can afford it, then I would suggest seriously considering going the LL route. You already have most of the stuff with you so it would not cost significantly more than your current setup, maybe an additional $200-$250.

Hope this helps.