Oh ye of little faith,
It turns out that the big plano lens will be the easiest lens to get by making it by hand. It will be the other lenses that will be hard because I would like them to have at least 150mm diameter. If it turns out that the lens can only be made for a reasonable cost by hand I will be making the lenses more like 250mm in diameter.
Perhaps you have not seen my other thread on the large hand made lens. The large plano convex will be hand made at a relatively low cost.
Here is a picture of the mold blank in it's current state.
Hezz
It turns out that the big plano lens will be the easiest lens to get by making it by hand. It will be the other lenses that will be hard because I would like them to have at least 150mm diameter. If it turns out that the lens can only be made for a reasonable cost by hand I will be making the lenses more like 250mm in diameter.
Perhaps you have not seen my other thread on the large hand made lens. The large plano convex will be hand made at a relatively low cost.
Here is a picture of the mold blank in it's current state.
Hezz
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Guys,
It is unlikely that any optical engineers are going to sit down with us to design a system of this complexity and a zoom lens system with high resloving power is far more complex than you might think. Here is a picture to give you an idea.
There are however a few differences in our design that can relax the design requirements considerably and that is that we don't need as much resolving power as a photographic zoom lens.
We only need to be able to resolve an image the size of the smallest pixel on an average LCD screen. Say .23mm.
In photographic film the lens needs to be able to resolve each minute dot which is several orders of magnitude smaller than we need. This is why photographic quality lenses are so expensive because the finer area the lens must resolve the more complicated it is because it must have lots of abberation correction.
Hezz
It is unlikely that any optical engineers are going to sit down with us to design a system of this complexity and a zoom lens system with high resloving power is far more complex than you might think. Here is a picture to give you an idea.
There are however a few differences in our design that can relax the design requirements considerably and that is that we don't need as much resolving power as a photographic zoom lens.
We only need to be able to resolve an image the size of the smallest pixel on an average LCD screen. Say .23mm.
In photographic film the lens needs to be able to resolve each minute dot which is several orders of magnitude smaller than we need. This is why photographic quality lenses are so expensive because the finer area the lens must resolve the more complicated it is because it must have lots of abberation correction.
Hezz
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I'm sorry hezz... but I really dont see your lens working anywhere near a high quality cut and ground lens. There is just too much involved in making a good lens and now you say it's easy... your hopes are way too high friend. Then theres coatings... which your lens wont have and is far from easy to do... and even if you did it yourself it still would be a sub-par lens.
Giant PCX lenses arent found anywhere because they are anything but easy to make!
There are other ways that would work better. Making your own giant lens... isnt one of them.
I hope you prove me wrong... but I doubt it 🙂
Giant PCX lenses arent found anywhere because they are anything but easy to make!
There are other ways that would work better. Making your own giant lens... isnt one of them.
I hope you prove me wrong... but I doubt it 🙂
How do you think the highest quality lenses are finished?
By hand. In fact PCX lenses are very cheap to make in large quantities because they are injection molded from plastic. But what keeps them cheap is the fact that they don't require much final finishing. The mold is made to such high standards that the final lenses need only a small polish.
The only reason large PCX lenses are not made is because plastic is not a stable enough for higher mass objects so a large PCX lens would have to have extensive grinding and polishing done to it. Due to shrinkage and other factors. However my manual method overcomes many of the technical factors which make mass produced large lenses impractical.
This raises the cost to where it has little advantage over glass.
The amature telescope makers routinly make hand ground mirrors which are superior to machine made lenses. The only setback is that they are work intensive to make.
The machines follow specific grinding and polishing procedures which can be duplicated by hand in many circumstances. The only lenses that we can't make by hand are aspheric lenses.
Besides if you don't wish to make the large lens you still use a fresnel which will work in the same way however with reduced imaging properties.
Hezz
By hand. In fact PCX lenses are very cheap to make in large quantities because they are injection molded from plastic. But what keeps them cheap is the fact that they don't require much final finishing. The mold is made to such high standards that the final lenses need only a small polish.
The only reason large PCX lenses are not made is because plastic is not a stable enough for higher mass objects so a large PCX lens would have to have extensive grinding and polishing done to it. Due to shrinkage and other factors. However my manual method overcomes many of the technical factors which make mass produced large lenses impractical.
This raises the cost to where it has little advantage over glass.
The amature telescope makers routinly make hand ground mirrors which are superior to machine made lenses. The only setback is that they are work intensive to make.
The machines follow specific grinding and polishing procedures which can be duplicated by hand in many circumstances. The only lenses that we can't make by hand are aspheric lenses.
Besides if you don't wish to make the large lens you still use a fresnel which will work in the same way however with reduced imaging properties.
Hezz
fresnels only reduce image quality if you use them split and place one in front of the lcd. I dont do this anymore since I got larger longer focal length fresnels... which solves the problem. When used like this, as light gathers, fresnels are the way to go.
JCB,
I have to admit that the longer focal length fresnels behind the LCD do make some sense. However, it seems like most DIYers want smaller projectors. But with say a nine inch first fresnel and an 24 inch second fresnel in front of the LCD and a large high quality objective that should work better.
The question is since you are losing some light due to the dispursive qualities of the LCD would the field lens reduce light output and imaging more than what would be lost from not collecting all of the light from the LCD. Remember that the OHP analogy will not hold completely true because the LCD disrupts the light paths to a significant degree therefore the fact that the light is focused from behind the LCD towards the objective does not mean that it will stay that way after passing the LCD.
Hezz
I have to admit that the longer focal length fresnels behind the LCD do make some sense. However, it seems like most DIYers want smaller projectors. But with say a nine inch first fresnel and an 24 inch second fresnel in front of the LCD and a large high quality objective that should work better.
The question is since you are losing some light due to the dispursive qualities of the LCD would the field lens reduce light output and imaging more than what would be lost from not collecting all of the light from the LCD. Remember that the OHP analogy will not hold completely true because the LCD disrupts the light paths to a significant degree therefore the fact that the light is focused from behind the LCD towards the objective does not mean that it will stay that way after passing the LCD.
Hezz
Hey Brainchild have you played with the soom lens anymore?
I was wondering if you tried a curved screen to help overcome some of the barrelling?
I was wondering if you tried a curved screen to help overcome some of the barrelling?
jcbklyny,
You have a double fresnel lens unsplit before the lcd? What size is it , and how much did you pay? You got it from Edmundoptics?
Hezz im going to make up a lens real soon, it will be alot easier to make then yours and i believe will work better, i also have 2 choices in the way of making it , i can make it like a stepping frensel or like a normal curved lens, no casting is also required, with yours being a plano convex is this meant to go infront the lcd? mine will go behind and will be a plano concave, i have a few chioces in how i want to make it but its easy to make and i dont have to cast it.
Trev
Trev
Trev, how easy is easy?
And are you talking about a small lens, as in for a 7" lcd, or would your "easy method" work for a large, 15" LCD sized lens as well?
Care to go into any more detail on your process?
And are you talking about a small lens, as in for a 7" lcd, or would your "easy method" work for a large, 15" LCD sized lens as well?
Care to go into any more detail on your process?
Found this, thought someone might find it interesting.
Its a chapter from an optics book about design and implementation of a cooke triplet. Although alot of it is way over my head, it was interesting to read.
http://www.willbell.com/tm/The Cooke Triplet and Tessar Lenses.pdf
Its a chapter from an optics book about design and implementation of a cooke triplet. Although alot of it is way over my head, it was interesting to read.
http://www.willbell.com/tm/The Cooke Triplet and Tessar Lenses.pdf
My fresnels arent from edmund... but AWI. They are 12.3 by 9.3 with rings from tip to tip. Perfectly even image.
I've also been fooling around outside the board for a while now and have come up with some NEW lenses for my project. From a new style condenser to a 4 element DIY projection lens with 360mm focal for a longer throw, brighter & sharper image at a normal size!. All of which is DONE 🙂 I'll have more info on it in coming weeks. Keep your eyes open!
www.diybuildergroup.com
soon!!
I've also been fooling around outside the board for a while now and have come up with some NEW lenses for my project. From a new style condenser to a 4 element DIY projection lens with 360mm focal for a longer throw, brighter & sharper image at a normal size!. All of which is DONE 🙂 I'll have more info on it in coming weeks. Keep your eyes open!
www.diybuildergroup.com
soon!!
How many groves per inch? Are you saying that if you compared these AWI fresnels with diylabs fresnels the results would be as follows:
Diylabs fresnels: hotspoting
AWI Fresnels: no hotspotting
diylabs fresnels are not 100 grooves per inch... they are 50 with a .5 pitch. diylabs fudges his numbers... so dont go by what he says. His triplets arent 80mm they are 63mm and I have yet to see his condensers just to name a few problems.
The biggest difference with high quality fresnels and square ohp style is the size of the lens itself. AWI singles dont have cut corners and because I had them custom cut mine... they are a perfect fit for my lcd. I can place them both behind the lcd and get a brighter, sharper image from corner to corner then I could with cheap diylabs or ohp fresnels. The rings extend from tip to tip so the entire fresnel is active. Unlike OHP fresnels.
And I'm not planning on selling fresnels so this has nothing to do with me!
www.diybuildergroup.com
soon
The biggest difference with high quality fresnels and square ohp style is the size of the lens itself. AWI singles dont have cut corners and because I had them custom cut mine... they are a perfect fit for my lcd. I can place them both behind the lcd and get a brighter, sharper image from corner to corner then I could with cheap diylabs or ohp fresnels. The rings extend from tip to tip so the entire fresnel is active. Unlike OHP fresnels.
And I'm not planning on selling fresnels so this has nothing to do with me!
www.diybuildergroup.com
soon
jcbklyny,
What about lighting eveness. Have you noticed a difference between the OHP fresnels and the AIW in terms of lighting evenness?
I realizer now there is no way I can keep my fresnels behind the lcd. The beam coming out the other end of the fresnel is narrowed so passing through the lcd it will pass through the middle of it only. If I was to keep the same FL fresnel arrangement my guess is I would need a back fresnel that is much larger. About 20 inches? Why do I feel mislead?
Splitting the fresnels and putting the lcd in between I get the most even lighting and with the 400 watt it will be more even but there will still be a fall of. I am pretty convinced. Find out tomorrow with the test I guess.
What about lighting eveness. Have you noticed a difference between the OHP fresnels and the AIW in terms of lighting evenness?
I realizer now there is no way I can keep my fresnels behind the lcd. The beam coming out the other end of the fresnel is narrowed so passing through the lcd it will pass through the middle of it only. If I was to keep the same FL fresnel arrangement my guess is I would need a back fresnel that is much larger. About 20 inches? Why do I feel mislead?
Splitting the fresnels and putting the lcd in between I get the most even lighting and with the 400 watt it will be more even but there will still be a fall of. I am pretty convinced. Find out tomorrow with the test I guess.
What size is your back fresnel ? How many grooves and pitch?
I assume this is a factor in light eveness also?
I assume this is a factor in light eveness also?
MovLab, http://www.awi-industries.com/Fresnels.html
Thanks, we've come up with some great new ideas for future designs.
Dracul, you want a low pitch for a fresnel being using in a condenser system (light collector w/ .5 pitch ideal). If you split fresnels, your optical system should have a top fresnel (or field fresnel) with a higher pitch count then the one underneath the LCD. (.3 pitch and under)
Most standard fresnels have a .5 pitch (50 grooves per inch). This includes the AWI singles I have. Where these are different is they are cut to the rectanglar lens, they are FLAT and have rings across the entire lens. So the entire fresnel is "active". OHP doubles (diylabs etc) are SQUARE, the corners are cut off and they have a lip so you cant use the entire lens (grooves dont go out to edge) and they are bowed. Big difference!
The optical setup of my system looks something like this:
spherical reflector
condenser
bottom fresnel - 8.95" focal / 225mm
top fresnel - 15.75" focal / 400mm
LCD
Enhanced Aluminum first surface mirror
Custom 4 element 360mm focal projection lens
You'll be able to find all the sizes, focals, spacing etc on the new site opening. But the lenses that made the biggest difference were the top fresnel with it's longer focal length, the new condenser and the new projection lens with longer focal. The 4 element lens isnt a triplet with an extra lens added either. It's something else 🙂
____________________
www.diybuildergroup.com
soon
Thanks, we've come up with some great new ideas for future designs.
Dracul, you want a low pitch for a fresnel being using in a condenser system (light collector w/ .5 pitch ideal). If you split fresnels, your optical system should have a top fresnel (or field fresnel) with a higher pitch count then the one underneath the LCD. (.3 pitch and under)
Most standard fresnels have a .5 pitch (50 grooves per inch). This includes the AWI singles I have. Where these are different is they are cut to the rectanglar lens, they are FLAT and have rings across the entire lens. So the entire fresnel is "active". OHP doubles (diylabs etc) are SQUARE, the corners are cut off and they have a lip so you cant use the entire lens (grooves dont go out to edge) and they are bowed. Big difference!
The optical setup of my system looks something like this:
spherical reflector
condenser
bottom fresnel - 8.95" focal / 225mm
top fresnel - 15.75" focal / 400mm
LCD
Enhanced Aluminum first surface mirror
Custom 4 element 360mm focal projection lens
You'll be able to find all the sizes, focals, spacing etc on the new site opening. But the lenses that made the biggest difference were the top fresnel with it's longer focal length, the new condenser and the new projection lens with longer focal. The 4 element lens isnt a triplet with an extra lens added either. It's something else 🙂
____________________
www.diybuildergroup.com
soon
What would you say is the single most important element that is responsible for you getting an evenly lit image on the screen?
Your fresnel is before the lcd correct? It is not split correct? How far is it from the lcd?
I can make my fresnels flat also just by putting them between glass. I tried this but this did not solve my hotspot issue.
If I leave my fresnel unsplit and before the lcd I get a spot light effect going through the lcd or only through the center. So I ask you how in the hell is this supposed to work? Even if you even out the light with a condenser you still get a spot light effect passing through the lcd. Have you tested the light eveness with and without condenser to see the amount of difference?
Your fresnel is before the lcd correct? It is not split correct? How far is it from the lcd?
I can make my fresnels flat also just by putting them between glass. I tried this but this did not solve my hotspot issue.
If I leave my fresnel unsplit and before the lcd I get a spot light effect going through the lcd or only through the center. So I ask you how in the hell is this supposed to work? Even if you even out the light with a condenser you still get a spot light effect passing through the lcd. Have you tested the light eveness with and without condenser to see the amount of difference?
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