Hello Ace
Just out of curiosity, is this the reflector you are using in your 2 condenser light engine, or have you gone with a different configuration? I'm only asking because I've been playing around with a 2-condenser setup as well but it will be used for a larger LCD. It's not very efficient at the moment because of stray light angles, but I'm working on it. My current thoughts are of using a hybrid spherical / parabolic reflector, but It might be too difficult to make.
DJ
Can be used in either a single condenser config or a duel condenser config, no diff and no stray light at all. Both reflectors work on the 2 condenser design, infact all should within reason and with minor ajustment.
Yeah im not sure if the duel condenser setup is ideal for a large lcd cos the latter condenser channels the light to the lcd and when we have that latter condenser, depending on focal ect, we are making the beam narrower to suit the lcds size but yet withholding the correct beam angle. Ill draw you a quick pic to show you what it actually does. Ill also mention the 2 condensers arent of the same spec.
Trev
yeah, thats what i figured. I'm haveing trouble finding a second condensor with the right focal and diameter.
DJ
Hers the pic, its miles out as light rays go and optical spacing as i drew this one fast, the beam on the second condenser is fully ajustible, we can even get the light to nearly paralelle, but this all depends on the combination of lenses used and the reflector focal ect to get those rays right. I dont use a pcx for the second condenser either, i use a acromat singlet and looking at trying a menscus. Finding the focal for each lens is the hard bit to get the light angles right, also the reflector, but after abit of fooling around, you have a bearing to go from, i have a bearing for mine and it works spot on, its just a matter of me finding another secondary condenser that performs the same as the acromat i have for you guys.
Trev
Trev
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For seeing how two lenses will work together, try using this....
http://webphysics.davidson.edu/Applets/Optics/Intro.html
It's pretty cool.
T.
http://webphysics.davidson.edu/Applets/Optics/Intro.html
It's pretty cool.
T.
It’s a Samsung Syncmaster 172 MP 17". I haven’t decided on the optical set up yet, I’m leaning towards using a condenser that produces close to parallel light, then reflected off a cold mirror and threw the second condenser. The second condenser needs to be about 90mm diameter with a 44mm FL to produce the desired focal angle for the fresnel. Trying to use a cold mirror without two condensers is very difficult when using a LCD of this size. Another reason I’m using parallel light is the fact that cold mirrors are the most efficient when all the light is striking it from 45 degrees.
Are you using the acromat for chromatic correction or for spherical correction or both? And how does if stand up to the heat?
DJ
Hello tgreenwood,
What a great little program. Save me getting headaches when I do ray traces in my head.
DJ
What a great little program. Save me getting headaches when I do ray traces in my head.
DJ
Ace, sorry for so may consecutive post, but the time differences between us suck.
Just so we are talking about the same thing, the acromat you are using is it the two lenses cemented together or a loose one? The meniscus might be good to use for first condenser too.
DJ
If it's possible to use only one condenser for the 15" LCDs (with a 220mm FL fresnel), what would its specs be, and where would it be positioned?
Dazzzla said:
Hmmm 90mm dia at a focal of 44mm? i doubt you will find that lens manufactured, probally have to get it custom made, id also be using that as the primary condenser and have a longer focal for the second to ajust your beam angle as thats prety much how they work.
I get what your saying on the pralelle light too, its prabally the same thing as what id try to do if i was using a cold mirror. As for the cold mirror, the cold mirror has to be a 45deg spec mirror for the rays to be working best at 45deg, a 0deg cold mirror works best at 0deg and transmits ir red forward while the reflected visible light gets reflected back. Ive attached a few pics for ya to have a look at, if i wer you, id use a negative pcx lens to be used as a diverger to spread the paralelle light rays over the lcd after the cold mirror, a negative frensel can also be used very efectively as whats in the pic. Im kind of short for words today, abit tyred i guess so i hope you know what i mean lol, if not just say so and ill elaborate.
As for the acromat, its a singlet acromat thats 2 lenses in 1, non cemented, chromatic aberation it does somwhat fix, but i dont have that problem to my eyes, one thing i did notice is the colour temp of the bulb went alot whiter and the image brightness went nearly 2x brighter on the cdm-t bulb, brighter then the par reflector design. That is also without the precision spherical so this idea has alot of potentional to even get more eficientcy out of the bulb, wich is somthing i want as id rather run a low heat and energy saving 150w compared to a energy abusing hot 250w. The 250w on this design ive had the same if not brighter then beforcades 400w which i think to me personally, is a breakthrough, i just wish i had the cam to prove my point.
Regarding in a previous post on asking if menscus lenses are fine, they are best for the secondary condenser while the first should be a pcx, pcx lenses are much brighter. In the duel condenser setup the most important thing to do first is to get the first condenser setup correctly in all aspects and brightness is one of them cos if the first condenser is out, the secondary will enhance the problems.
Trev🙂
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Heya Scott, if youve got a 250w hqi bulb then a diameter of 65 - 90mm with a 114mm focal condenser will do you fine, shorter focals are better if you want some more brightness and will spread the light at a wider angle. Having a condenser too big will flood the condenser with light and having a condenser too small will not collect enough light, 80mm is about ther max you would realy want to go on a hqi 250w's beams pattern. I have a couple of 80mm dia condensers here with a focal of 87mm that work great, unfortunatley they cant be used in this design as a duel condenser setup yet, hence why they are sitting around.
Trev🙂
Hello ScottK
Adding a condenser to your light engine with the values you have would be very difficult to calculate.
With a lcd of 381mm and fresnel fl of 220mm, the beam angle required by the fresnel would be about 81 degrees and the angle of incidence would be half this, 40.5 degrees. When light strikes a lens it can do two main things, refract or reflect. The thing that determines how much reflection and how much refraction that will occur, is called the angle of incidence. As the angle of incidence becomes bigger, more light is reflected and less refracted until a point is reached where total reflection takes over, this is called the critical angle and its value is about 41 degrees. So in this situation you’re at about the most efficient position without using a condenser. Condensers a good for improving the situation when the fresnel fl is larger than half the its dimensions, as in Ace’s setup.
This is all theory, so don’t take it as gospel, theory and practise doesn’t always agree. I’m not an expert on optics either, I’ve had no formal education in optical engineering, and all the information above came from reading lots. So if something isn’t correct someone let me know.
DJ
Ace you bet me to it, Should have checked before I posted.
Adding a condenser to your light engine with the values you have would be very difficult to calculate.
With a lcd of 381mm and fresnel fl of 220mm, the beam angle required by the fresnel would be about 81 degrees and the angle of incidence would be half this, 40.5 degrees. When light strikes a lens it can do two main things, refract or reflect. The thing that determines how much reflection and how much refraction that will occur, is called the angle of incidence. As the angle of incidence becomes bigger, more light is reflected and less refracted until a point is reached where total reflection takes over, this is called the critical angle and its value is about 41 degrees. So in this situation you’re at about the most efficient position without using a condenser. Condensers a good for improving the situation when the fresnel fl is larger than half the its dimensions, as in Ace’s setup.
This is all theory, so don’t take it as gospel, theory and practise doesn’t always agree. I’m not an expert on optics either, I’ve had no formal education in optical engineering, and all the information above came from reading lots. So if something isn’t correct someone let me know.
DJ
Ace you bet me to it, Should have checked before I posted.
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Actually i should correct myself here lol i meant to say a negative PCV ( plano concave ) lens.
Trev
Trev
Hello Ace
The reason I suggested using a menicus as the first condenser is that I think it might be able to collect more light from the lamp. As I explained in my last post to ScottK, The critical angle might be a limiting factor when we use condensers so close to a lamp. This is only a theory, I haven’t actually tested it yet. Any thoughts on this idea?
Here is a pic to help explain what I mean.
DJ
The reason I suggested using a menicus as the first condenser is that I think it might be able to collect more light from the lamp. As I explained in my last post to ScottK, The critical angle might be a limiting factor when we use condensers so close to a lamp. This is only a theory, I haven’t actually tested it yet. Any thoughts on this idea?
Here is a pic to help explain what I mean.
DJ
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Heya Daz, not sure, i doubt it cos that depends on the size of the condenser and the coating for a comparison, but i will say this, a menscus lens reflection reflects light back somwhat back to its source, also ( this is where there might be confusion about gathering more light) if you take a look at your drawing the menscus lenses outer edge is closer to the bulb then a pcx, this changes the distance of the outer light rays has to travel wich in turn could give you a more even image, though they do have way high distortion levels and a lack of magnifacation. Even though the outer edge is closer to the light rays on the outer edges we have a problem, its further on the otherside meaning its a further distance to the outer edges of our frensel, and thats where the distortion kicks in, and thats why we use a pcx. Ive got a few menscus lenses here that ive tried and by far the pcx gives no troubles and a high performance image over any menscus ive owned. You can use aspheric lenses aswell, they work very well but not so cheap.
Ive been reading in my optical book today and ive just worked out how to offset a focal axis, meaning ive just learnt how to create the so called "image shift" function.🙂
Trev
Ive been reading in my optical book today and ive just worked out how to offset a focal axis, meaning ive just learnt how to create the so called "image shift" function.🙂
Trev
That was one of my thoughts as well, but hey it’s only theory. As for an aspheric, that’s my next experiment. I’ve actually got quite a few of these, they came from late modal cars headlights but I’m not to sure of their quality, could have potential if it’s matched up with the right reflector.
That would be cool if you could get it working. Hard to do with small lenses isn’t it?
DJ
heya bud, yep they would work, (ofcourse depending on specs), just make sure they arent plastic so they dont melt up lol.
Actually its very simple, the only problem is what we need only comes in small sizes so ill have to have a hunt around for a bigger one or take a look at how to impliment it in a triplet, probally put it after the dcv or somthing.
Trev
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