Well, it seems to be the latest delema here on diy audio... A fresnel lens that will cover a 15" lcd monitor. Many people here have simply gone with a 12"x12" ohp fresnel, and had the edges of there lcds cut off. Works well for 16:9 movies, but for 4:3, you have to resize your image to fit... I dont think so... I want the entire 15" of my nec monitor! So, Its 12:00 and I am going fresnel hunting. I came across another thread that had a tv magnifier. It turnes out this is a 2X fresnel that you place in from of you tv and boom... 36" diagnol... That one was way too big for diy projectors. I did some searching and came across an afordable website selling these 2X magnifier fresnels in smaller sizes.
Whats the price tag? $34.95 for the small size, and $39.95 for the medium size. This leaves on question though? Is 2X magnification enough?
http://www.optelec.com/ProductDisplay.asp?ProductID=140
I am going to email them and ask about the size that will cover a 15" lcd screen. The think the one mad for 12" screens will work just fine 🙂
Later Guys,
Phil
Whats the price tag? $34.95 for the small size, and $39.95 for the medium size. This leaves on question though? Is 2X magnification enough?
http://www.optelec.com/ProductDisplay.asp?ProductID=140
An externally hosted image should be here but it was not working when we last tested it.
I am going to email them and ask about the size that will cover a 15" lcd screen. The think the one mad for 12" screens will work just fine 🙂
Later Guys,
Phil
Yeah, that link has been posted here quite a few times. Someone tried it and it didn't work. The focal lenght of that thing is like 30" or something like that. Also, it's a single, not a double. However, two of them might work, if we can find one that has a shorter focal lenght (unlikely). Those things are made out of thin plastic, not thick acrylic, so I think the bulb would melt it. Not sure on that though.
I think I may have found one way to solve the problem.
I found a company that would cut one of their stock 15" dia. fresnels to an effective size of 12"x9" with a 14" focal length. That would work great for the top fresnel... but the bottom one would have to be custom made for a shorter focal length. I'm working on bulk pricing to try and sell these as a package to board members... so I'll keep everyone updated.
BTW... these won't be cheap... so anyone who is trying to solve this for 50 bucks can forget it!
But this IS a solution.
I found a company that would cut one of their stock 15" dia. fresnels to an effective size of 12"x9" with a 14" focal length. That would work great for the top fresnel... but the bottom one would have to be custom made for a shorter focal length. I'm working on bulk pricing to try and sell these as a package to board members... so I'll keep everyone updated.
BTW... these won't be cheap... so anyone who is trying to solve this for 50 bucks can forget it!
But this IS a solution.
One more thing...
I would only make these available for 15" LCD's including widescreen models.
17" and above are out of the question for a number of different reasons.
I would only make these available for 15" LCD's including widescreen models.
17" and above are out of the question for a number of different reasons.
jcbklyny said:
Great idea, man. I was thinking of it already, but I can't do much about being a reseller for custom-made fresnels as I'm in Russia. I though came across with www.display-optics.com, they produce fresnels of some standard sizes, offer custom designs, but require to order 25 pcs. minimum.
The only thing I would suggest you is to make fresnels a bit bigger so they would fit not only 15" LCD, but 15,1" also.
The second thing that the shorter focal length fresnels should have exactly the same resolution (grooves per inch) as the standard 14" FL ones. In this case one could combine these two types of lenses to work together.
Is there any benefit to cutting a fresnel to a rectangular shape? I mean, wouldn't a 12x9 inch fresnel lose the same amount of light as a 12x12 fresnel? Doesn't it have to do with the rings or something?
Benefit is the possibility of a smaller design. 12x9 will work almost exactly as 12x12 one (I think it can work even better because the unused areas of the bigger fresnel, if not masked, can wash out the picture to some extent).Lifter said:
Some more info on those fresnels...
Now they both are going to be customs. The standard fresnels have too low a groove per inch count. My customs are going to have focal lengths of 14" for the top and 10" on the bottom... with 200 Grooves per inch on each one! Besides the high price of being custom made... these should be PERFECT for the project.
And they will NOT be doublets... they will be 2 single fresnels as I perfer the "sandwich method".
-John
Now they both are going to be customs. The standard fresnels have too low a groove per inch count. My customs are going to have focal lengths of 14" for the top and 10" on the bottom... with 200 Grooves per inch on each one! Besides the high price of being custom made... these should be PERFECT for the project.
And they will NOT be doublets... they will be 2 single fresnels as I perfer the "sandwich method".
-John
Ditto.
And BTW, 13" would be perfect for a 15" panel. 12" is ever-so-slightly too small. If you having it custom made anyways, would 13" fly?
And BTW, 13" would be perfect for a 15" panel. 12" is ever-so-slightly too small. If you having it custom made anyways, would 13" fly?
Sure I could... but an extra inch is alot of space. I think you would get better results if the optics were perfectly aligned rather then oversized. I want the case to be as tight as possible.
I'll have a price on monday.
Plus I'll add that this was the first company out of dozens I spoke with that wanted to know exactly how the fresnels would be used so that they could be designed to do the job right. Light source, position etc... Everyone else seemed like they didnt care what I did with them.
-John
I'm also looking for bulk orders on Front surface mirrors & UV/IR heat glass... this way I can offer harder to get high quality DIY items.
I'll have a price on monday.
Plus I'll add that this was the first company out of dozens I spoke with that wanted to know exactly how the fresnels would be used so that they could be designed to do the job right. Light source, position etc... Everyone else seemed like they didnt care what I did with them.
-John
I'm also looking for bulk orders on Front surface mirrors & UV/IR heat glass... this way I can offer harder to get high quality DIY items.
Once I order a standard sized 15" I'll be able to see whether or not it's worth it to start ordering different sizes. As it is I dont think that many people will be willing to drop as much as these customs are going to cost.
Dont get me wrong, they wont be more then any other large quality fresnel out there... but the board seems to be filled with people would just dont want to spend the money.
Dont get me wrong, they wont be more then any other large quality fresnel out there... but the board seems to be filled with people would just dont want to spend the money.
You still haven't told us how much. So, how much? You'd be surprised what I'd be willing to spend, provided that I know what I'm getting and it's something I need.
I would be willing to spend $100+ on a good quality fresnel that will do the job right on a 15" lcd panel. All I need is advanced notice so I can have my thugs print out some more cash 😀 . I am really at the point now where this is a project of love, and not so much cheaping out to save cash.
Well, gui_99 might be out of luck 🙂
I'm getting a final SET price later on this afternoon... but I'm having the customs made up as singles... not doubles. And each one will be more then a hundred bucks a piece without a doubt.
You have to compare them to any other high quality fresnel you'll find online. You'll find some really nice... expensive fresnels! But not one of them will have the specs that these customs will. A 12x9 effective area with 200 grooves per inch, 2 different focal lengths and 2 different purposes? The 10" focal length is being designed as a collimator... the 14" as a collector.
You won't find it!
Although fresnel lenses arent really recommended in imaging... these are being designed with imaging in mind. What we're all looking for!
I know people are looking for a cheaper way out of this, but I've looked... and I just dont see us getting the picture quality we want any other way.
-John
I'm getting a final SET price later on this afternoon... but I'm having the customs made up as singles... not doubles. And each one will be more then a hundred bucks a piece without a doubt.
You have to compare them to any other high quality fresnel you'll find online. You'll find some really nice... expensive fresnels! But not one of them will have the specs that these customs will. A 12x9 effective area with 200 grooves per inch, 2 different focal lengths and 2 different purposes? The 10" focal length is being designed as a collimator... the 14" as a collector.
You won't find it!
Although fresnel lenses arent really recommended in imaging... these are being designed with imaging in mind. What we're all looking for!
I know people are looking for a cheaper way out of this, but I've looked... and I just dont see us getting the picture quality we want any other way.
-John
can you contact me via email and give me a little more information about these fresnels you are having made, and the use they are going to be intended for. Im really interested in this, adn price is not reall an issue as long as it does the job well. If the thing is $200 though, i'll have to think about it. $100+ range is fair-ok. How many compainies are you contacting about these making custom fresnels?
well if I understand, it will be 200$ and more. If it's more than 100$ a piece like he sais.. 2 will be more than 200$
Before i slap down *small* bucks
I just want to get this straight from "current" thread posters before i slap down what i hope will be small bucks because i seem to be getting a range of conflicting ideas from reading past posts on different threads:
This is the basic configuration that most of you are looking at:
Light source ----> double fresnel ---->
LCD----> projection lens-----> screen
Is that right?
Where the double fresnel looks like this:
light source ---> fresnel which makes the light rays parallel----> fresnel which converges the parallel light rays which then go through the lcd and converge slightly further than the projection lens
right?
Also i read that there are what are called "positive" and "negative" fresnels and you cannot use only one type for the two fresnels above...in other words one of those above fresnels have to be "positive" and the other one has to be "negative" and you cannot just flip over a "positive" fresnel to act like a "negative" fresnel... right?
Also, from what i gather the following setup is not so good because it degrades image quality...
lightsource---> fresnel which makes parallel rays----> LCD -----> Fresnel which makes parallel rays converge ----> Projection lens
right?
Also from what i see most people are using a simple lens from an OHP for the projection lens...but i don't see too many people using a manufactured projection lens made for things like film projectors (the kind of lens that looks like a tube with like "kodak" written on the tube)...why is that?
thanks
I just want to get this straight from "current" thread posters before i slap down what i hope will be small bucks because i seem to be getting a range of conflicting ideas from reading past posts on different threads:
This is the basic configuration that most of you are looking at:
Light source ----> double fresnel ---->
LCD----> projection lens-----> screen
Is that right?
Where the double fresnel looks like this:
light source ---> fresnel which makes the light rays parallel----> fresnel which converges the parallel light rays which then go through the lcd and converge slightly further than the projection lens
right?
Also i read that there are what are called "positive" and "negative" fresnels and you cannot use only one type for the two fresnels above...in other words one of those above fresnels have to be "positive" and the other one has to be "negative" and you cannot just flip over a "positive" fresnel to act like a "negative" fresnel... right?
Also, from what i gather the following setup is not so good because it degrades image quality...
lightsource---> fresnel which makes parallel rays----> LCD -----> Fresnel which makes parallel rays converge ----> Projection lens
right?
Also from what i see most people are using a simple lens from an OHP for the projection lens...but i don't see too many people using a manufactured projection lens made for things like film projectors (the kind of lens that looks like a tube with like "kodak" written on the tube)...why is that?
thanks
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