Hi folks, I've been bustin my own @$$ just to figure this out. Let me give a brief explanation about my setup.
1. 400watt MH lamp
2. 12'2"x12,2" dual focus (220mm & 330MM) fresnel in split configuration.
3. 15" LCD
4. 320mm Triplet.
And here's how I place it.
Lamp---(190mm)--->220mm FL fresnel---(20mm)--->15" LCD---(20mm)--->330mm FL fresnel---(Tried various distance)--->320mm Triplet.
Now the problem is when I watch movies through my DVD player, everything seems to look okay, even perfect. But when I use my computer to display images, I found out that the corners just won't focus. I use NOKIA monitor test. The center area is perfectly focused, the problem lies on each corner of the image. It won't 100% focus. Is this because the limitation of the triplet, or my design till has a flaw on it ? Could anybody here give further explanation ?
1. 400watt MH lamp
2. 12'2"x12,2" dual focus (220mm & 330MM) fresnel in split configuration.
3. 15" LCD
4. 320mm Triplet.
And here's how I place it.
Lamp---(190mm)--->220mm FL fresnel---(20mm)--->15" LCD---(20mm)--->330mm FL fresnel---(Tried various distance)--->320mm Triplet.
Now the problem is when I watch movies through my DVD player, everything seems to look okay, even perfect. But when I use my computer to display images, I found out that the corners just won't focus. I use NOKIA monitor test. The center area is perfectly focused, the problem lies on each corner of the image. It won't 100% focus. Is this because the limitation of the triplet, or my design till has a flaw on it ? Could anybody here give further explanation ?
OK what Im thinking is when your watching a DVD your seeing a letterboxed image and your not seeing a Blur because the Image is in the center of the lcd and thus lens. When you use the computer your using ALL of the lcd so the edges are unfocused I think that this was resolved with using a split fresnell...........But others will post Im sure 🙂
Yea, that is very right buddy. I'm using split design too, and my field lens it 100% flat. What's with that unfocused corners anyway ???
Yup, more or less. I've tried movind the LCD to 15mm to condenser fres and still in 20mm to filed. Still a no go. Please can you give me a clue ?
heya Dewil its from your lamp being too close to your frensel, or your condenser is causing the light to shadow the frensel rings on the corners, meaning your light is at an incorrect angle going to the lcd. Ajust your light to rear frensel focal and it will fix the prob.
Trev
I've tried moving the condenser to 220mm according to it's FL ace. Still a no go. My guess is the diameter of the triplet is to small. About 60mm. Correct me if I'm wrong please.
Hi Dewil,
I think the splitted fresnel could be the problem.
Try to put both fresnel together before the LCD. You may want to adjust the lamp distance according the new total FL on the Fresnel set.
The problem with a second fresnel lens in the image path is that it may produce aberrations, color shifts and unfocused corners due the fresnel is just a simple plano convex lens optimised in size.
Your projection lens is a 3 lenses system accurately calculated and optimized to solve all this aberrations produced by each single lens. Adding another lens to the system may carry such aberrations.
Sometimes is better to let the triplet do all the image projection job and use the unsplitted fresnell just to do all the lighting job. I think once the image is formed you must use only precision lens to get the best result. Cheap fresnell lens is not a good idea on the image path, but is a must in the light path before the LCD in order to lit all the display evenly and concentrate the light beam on the projection lens.
Is true that a splitted setup may offer a better colimatted light passing through the LCD and so better contrast, but I think this does not serve too much if the 2nd fresnel introduce aberrations on the projected image.
All this depends on fresnels quality and specs on all the system.
Just try it unsplitted to see if this is your case and let us know.
Best regards,
Bernardo.
I think the splitted fresnel could be the problem.
Try to put both fresnel together before the LCD. You may want to adjust the lamp distance according the new total FL on the Fresnel set.
The problem with a second fresnel lens in the image path is that it may produce aberrations, color shifts and unfocused corners due the fresnel is just a simple plano convex lens optimised in size.
Your projection lens is a 3 lenses system accurately calculated and optimized to solve all this aberrations produced by each single lens. Adding another lens to the system may carry such aberrations.
Sometimes is better to let the triplet do all the image projection job and use the unsplitted fresnell just to do all the lighting job. I think once the image is formed you must use only precision lens to get the best result. Cheap fresnell lens is not a good idea on the image path, but is a must in the light path before the LCD in order to lit all the display evenly and concentrate the light beam on the projection lens.
Is true that a splitted setup may offer a better colimatted light passing through the LCD and so better contrast, but I think this does not serve too much if the 2nd fresnel introduce aberrations on the projected image.
All this depends on fresnels quality and specs on all the system.
Just try it unsplitted to see if this is your case and let us know.
Best regards,
Bernardo.
hi dewil,
i try to explain why it won't work.
each objective has a specific field of view and the diagonal of the 15 incher doesn't fit into this field of view.
many people had those probs coz the objectives fl has to be at least the diagonal of the screen. look your screen has 15" ( maybe the real diagonal is 14.5") . that are 14.5" x 2.54 = 368 mm. Ur lens has an fl of 320mm. the distance to get a sharp image is 368mm plus 20-40mm( that ist the expierience) . so your lens has a fl is abit to short. 330 or 340 mm will work fine.
ief
i try to explain why it won't work.
each objective has a specific field of view and the diagonal of the 15 incher doesn't fit into this field of view.
many people had those probs coz the objectives fl has to be at least the diagonal of the screen. look your screen has 15" ( maybe the real diagonal is 14.5") . that are 14.5" x 2.54 = 368 mm. Ur lens has an fl of 320mm. the distance to get a sharp image is 368mm plus 20-40mm( that ist the expierience) . so your lens has a fl is abit to short. 330 or 340 mm will work fine.
ief
I eat flowers that very much could be the case. Ive had an issue like this in mine with the copy lens, sure the image is evenly lit and bright when the bulb is at the rear frensels focal but the sides of the image are slighly blured, to see this all you need is to make up a quick test screen thats filled full of fine text.
The problem arises from this: the copy lenses focal is 240mm, the top frensels focal is 310mm, oh no, a miss match, ok thats well known to me before i even started my design but i realy didnt think it would make that much of a diff, though imo its not noticable until you get right upto the screen.
The fix for this is to move your light back, well to be honest there isnt realy any fix other then finding a frensel thats got a top focal of 240mm. The only way to get a perfect edge distorion free ( in this case) image is to move the light back, when we move the light back out of the rear frensels focal it changes the angle of the top frensels light to a shorter gathering point to match the copy lens focal, and thats how we take away that distorion. But doing this the image becomes dull and the frensels arent working in their correct manner as your forcing light through the top frensel ( together or not ) at an incorect angle, so the best thing to do is to get a projection lens to suit your top frensels focal cos if not, you will have issues.
Having the frensels split can be brighter also, though its a diff brightness and to be honest somtimes its better, the abberations having them split isnt a problem if your light engine is setup right and if the frensel is atleast 10mm from the lcd. Having the frensels together actually makes the lcd run hotter as the light isnt going through the lcd in a paralelle manner, but having the frensels together seems to give the best results over all sources rather then just certain ones having them split. For example: frensels together are less bright on movies but hell bright in vga, having split frensels arent bright in vga and are much brighter in video, thats an example that ive found.
Hoped it helped
Trev
The problem arises from this: the copy lenses focal is 240mm, the top frensels focal is 310mm, oh no, a miss match, ok thats well known to me before i even started my design but i realy didnt think it would make that much of a diff, though imo its not noticable until you get right upto the screen.
The fix for this is to move your light back, well to be honest there isnt realy any fix other then finding a frensel thats got a top focal of 240mm. The only way to get a perfect edge distorion free ( in this case) image is to move the light back, when we move the light back out of the rear frensels focal it changes the angle of the top frensels light to a shorter gathering point to match the copy lens focal, and thats how we take away that distorion. But doing this the image becomes dull and the frensels arent working in their correct manner as your forcing light through the top frensel ( together or not ) at an incorect angle, so the best thing to do is to get a projection lens to suit your top frensels focal cos if not, you will have issues.
Having the frensels split can be brighter also, though its a diff brightness and to be honest somtimes its better, the abberations having them split isnt a problem if your light engine is setup right and if the frensel is atleast 10mm from the lcd. Having the frensels together actually makes the lcd run hotter as the light isnt going through the lcd in a paralelle manner, but having the frensels together seems to give the best results over all sources rather then just certain ones having them split. For example: frensels together are less bright on movies but hell bright in vga, having split frensels arent bright in vga and are much brighter in video, thats an example that ive found.
Hoped it helped
Trev
Dewil try this, take your condenser out, place the lamp back to the frensels focal, make sure the lamps arc is at the frensels focal and make sure its all centerd. Now make up a totally white screen in paint shop pro and palce black text in each corner top and bottom, and center.
Now move your light back until the letters of the outer text matches that of the center, ( sharpness and focal), dont worry you will never get it the same as the light travels at a diff angle when having frensels together however you can get it perfect having them split. Now measure the distance the light has gone past the rear frensels focal point, that will then be how far out the projection lens is to the top frensel, add that distance to your projection lenses focal, get a new peojection lens with that added, and your set to run a perfect projection with the light at the rear frensels focal and with the maximum brightness.
Example:
We have a 320mm focal triplet
a 220mm focal rear frensel
and a 330mm focal top frensel
say you want a 100inch diag image
Ok at this size the sides of the image blur, the focal of the triplet is out to the top frensels focal so... we move the light back to get the image perfect, it will be around 20mm ( condensers are taken out while doing this!). So the light is back 20mm more then it should be on the rear frensel, add this to the triplets focal wich becomes 340mm. Get a triplet thats 340mm and then place the light back at the rear frensels focal and you should have a perfect image with only very minor ajustment to spare.
In pro projectors its very diff, they have a lens thats staionary to collect light from the frensel, we dont, and im not going to get into this cos this post is long as it is and id have to basically write a whole book on how their lenses work. To give you a hint, in pro projectors projection lenses they have a feild lens at the back, that stays stationary while the 4 internal front elemants are the ones that move for the zoom and focus feature, that way they dont have an issue on changing a focusing point from the frensel as we do. Most modern pro projectors have their light going in a paralelle manner to their projection lenses also ( cos they have such small panels they can) and this eliminates that problem altogether.
With your projection lens only being out the 10mm from the top frensels focal it does create a problem but only a very small one, as i said , try moving your light back and you will surley see the diff, the trade off? miss matched optics and light loss though in your setup that should be very minimal if not noticable.
Now the condenser, you need a condenser to match the rear frensels focal, typicaly its half of the rear frensels facal to give you aceptiple results, however, if you want a brighter image get a condenser 1/4 of the frensels focal and add another condenser over that thats 1 - 2x the frensels focal to guide the light to the frensel at the correct angle, this gets tricky but its worth it as we utilise more light and get a 20 - 30% gain in image brightness. Make sure the light stays at the frensels rear focal at all times while adding any condenser or you will find you will have abberations and distorion again in your image and you are back to square 1.
Trev
Now move your light back until the letters of the outer text matches that of the center, ( sharpness and focal), dont worry you will never get it the same as the light travels at a diff angle when having frensels together however you can get it perfect having them split. Now measure the distance the light has gone past the rear frensels focal point, that will then be how far out the projection lens is to the top frensel, add that distance to your projection lenses focal, get a new peojection lens with that added, and your set to run a perfect projection with the light at the rear frensels focal and with the maximum brightness.
Example:
We have a 320mm focal triplet
a 220mm focal rear frensel
and a 330mm focal top frensel
say you want a 100inch diag image
Ok at this size the sides of the image blur, the focal of the triplet is out to the top frensels focal so... we move the light back to get the image perfect, it will be around 20mm ( condensers are taken out while doing this!). So the light is back 20mm more then it should be on the rear frensel, add this to the triplets focal wich becomes 340mm. Get a triplet thats 340mm and then place the light back at the rear frensels focal and you should have a perfect image with only very minor ajustment to spare.
In pro projectors its very diff, they have a lens thats staionary to collect light from the frensel, we dont, and im not going to get into this cos this post is long as it is and id have to basically write a whole book on how their lenses work. To give you a hint, in pro projectors projection lenses they have a feild lens at the back, that stays stationary while the 4 internal front elemants are the ones that move for the zoom and focus feature, that way they dont have an issue on changing a focusing point from the frensel as we do. Most modern pro projectors have their light going in a paralelle manner to their projection lenses also ( cos they have such small panels they can) and this eliminates that problem altogether.
With your projection lens only being out the 10mm from the top frensels focal it does create a problem but only a very small one, as i said , try moving your light back and you will surley see the diff, the trade off? miss matched optics and light loss though in your setup that should be very minimal if not noticable.
Now the condenser, you need a condenser to match the rear frensels focal, typicaly its half of the rear frensels facal to give you aceptiple results, however, if you want a brighter image get a condenser 1/4 of the frensels focal and add another condenser over that thats 1 - 2x the frensels focal to guide the light to the frensel at the correct angle, this gets tricky but its worth it as we utilise more light and get a 20 - 30% gain in image brightness. Make sure the light stays at the frensels rear focal at all times while adding any condenser or you will find you will have abberations and distorion again in your image and you are back to square 1.
Trev
Woooohoooo....Proffesor ACE has done it again 😀
Well first of all I'm NOT using a condenser and my lamp's arc is not in the rear fresnel focal (220mm). Why ? Because when I put it in the rear fresnel focal, the corners will become noticeably dimmer than the center. So I move it about 30mm backward. In this range, I get brightness corners to corners. And I'm NOT using a condenser.
I have that 342mm triplet from tony. I've tried that too. Still, I JUST CANT GET THE CORNERS TO FOCUS.
When I watch movies.....whoooaa just like having thousands of dollars plasma TV on my wall. Bright and perfectly focused. But when I pluged in my computer......
you know what happen to the corners right.......It's not too blurry though, but I just can't get it to focused like the corners. If I want to make the corners better focused (by moving the triplet), I must let go the 100% focused corners. To put it simple, if the center is 100% focused the corners are 60% focused. If I make the corners to 75-80% focused, the center will be 80% focused. And no matter how hard I try, I can't get the corners to 100% focused. Man, if this is the case, then this DIY PJ could only be use to watch movies not computer.
Hey ACE, how about that Lilli. Will it give 100% perfect focus center and corners ??? PLEASE.....what else should I try ???
Well first of all I'm NOT using a condenser and my lamp's arc is not in the rear fresnel focal (220mm). Why ? Because when I put it in the rear fresnel focal, the corners will become noticeably dimmer than the center. So I move it about 30mm backward. In this range, I get brightness corners to corners. And I'm NOT using a condenser.
I have that 342mm triplet from tony. I've tried that too. Still, I JUST CANT GET THE CORNERS TO FOCUS.
When I watch movies.....whoooaa just like having thousands of dollars plasma TV on my wall. Bright and perfectly focused. But when I pluged in my computer...... you know what happen to the corners right.......It's not too blurry though, but I just can't get it to focused like the corners. If I want to make the corners better focused (by moving the triplet), I must let go the 100% focused corners. To put it simple, if the center is 100% focused the corners are 60% focused. If I make the corners to 75-80% focused, the center will be 80% focused. And no matter how hard I try, I can't get the corners to 100% focused. Man, if this is the case, then this DIY PJ could only be use to watch movies not computer. Hey ACE, how about that Lilli. Will it give 100% perfect focus center and corners ??? PLEASE.....what else should I try ???
heya dewil ok lets take a look at a few other things but firstly i can tell ya now its definatley your frensels, failure to get the light at the focal point in the rear frensel will give you what you have.
Ok lets try this, have you got the frensels the right way around? if unsure, take them out, turn a light on in the room, focus the light on a table with the frensel halfs both seperately and see which has the shorter distance from the table, the one with the shorter distance is your rear frensel.
Scenario 2, are your frensels flat? if not thats the prob.
Scenario 3, are you using a reflector? if yess, what type? (soup laddle, precision spherical, parabollic ect.)
As for the lilliput, ive had this issue before and thats how i know what your problem is lol, normally on smaller screens its harder to fix errors as the movments must be small and everything is magnified 2x more then a large lcd, so they can be a chellenge. i have all mine sorted out now so no probs.
Trev🙂
Ok lets try this, have you got the frensels the right way around? if unsure, take them out, turn a light on in the room, focus the light on a table with the frensel halfs both seperately and see which has the shorter distance from the table, the one with the shorter distance is your rear frensel.
Scenario 2, are your frensels flat? if not thats the prob.
Scenario 3, are you using a reflector? if yess, what type? (soup laddle, precision spherical, parabollic ect.)
As for the lilliput, ive had this issue before and thats how i know what your problem is lol, normally on smaller screens its harder to fix errors as the movments must be small and everything is magnified 2x more then a large lcd, so they can be a chellenge. i have all mine sorted out now so no probs.
Trev🙂
Yes ACE, my fresnel is right at their "supposed to be" position. The 220 is for the condenser, the 330 is for the field. And yes, my fresnel is flat especially the field lens. The condenser is not as flat as the field lens, but I sandwiched it between glass. So it's flat now.😉
Ace, when I put the lamp at 220mm from the condenser, the corners of the projected image will become noticeably dim. So I move it a bit. Allthough in that 220mm range, still I got the same problem.
Okay guyz, so now the plot has thickens. Based on your info (thanks ACE, bfourcade, I_EAT_FLOWERS, and everybody I really appreciate it !!) I assume that :
YOU CAN NOT AND WILL NOT GET FOCUSED CORNERS IN THE COMMON 15" SETUP WITH COMMON 320MM TRIPLET LIKE MINE.
Please....let me say it again....please.....correct me if I'm wrong.
Any other info or even PROOFS of pictures that you can definiatelly get focused corners using this common setup is very very welcome....
PS : Geezzz......I really look that desperate ain't I ?? 😀
Ace, when I put the lamp at 220mm from the condenser, the corners of the projected image will become noticeably dim. So I move it a bit. Allthough in that 220mm range, still I got the same problem.
Okay guyz, so now the plot has thickens. Based on your info (thanks ACE, bfourcade, I_EAT_FLOWERS, and everybody I really appreciate it !!) I assume that :
YOU CAN NOT AND WILL NOT GET FOCUSED CORNERS IN THE COMMON 15" SETUP WITH COMMON 320MM TRIPLET LIKE MINE.
Please....let me say it again....please.....correct me if I'm wrong.
Any other info or even PROOFS of pictures that you can definiatelly get focused corners using this common setup is very very welcome....
PS : Geezzz......I really look that desperate ain't I ?? 😀
LOL i thought the same thing just the other week actually about the copy lens i use, but its not true, you can and will get it perfect, its not the triplet, its the light thats going to it, the light on the outer edges of the frensel is smudged making the image look out of focus when its realy not, thats the frensels doing and thats where we have to find a solution for you.
Any diff without the glass on the frensel? lol
Ill also mention this, maybe your frensel isnt realy 220mm focal, maybe its 230mm, normally they come in matched sets with the same numbers usually 100mm less on the rear frensel unless orderd specifically to be an odd number like yours, where you buy em from?
Trev
Hiya Ace, yea, I think that smuged light on the corners might be the probs. If this is the case, then the bigger fres like the one Alan sold could solve this ??? Maybe ??
Anyway, I got my fres from Tony Dean. And the FL is 220mm. I've tried that lamp in the room method to measure my focals.
Any other solution I should try ?
Anyway, I got my fres from Tony Dean. And the FL is 220mm. I've tried that lamp in the room method to measure my focals.
Any other solution I should try ?
K, have you tried having the both frensel together? maybe your distance between the 2 frensels is altering things, try to make the distance smaller and see how it goes.
Trev
Trev
That I have thought also. Ive tried this distances with the LCD :
1. 15mm to BF 20mm to FF.
2. 20mm to BF 20mm to FF.
3. 20mm to BF 25,20,25,40mm to FF.
(BF = Bottom Fresnel, FF = Field Fresnel).
Still a no go. Please don't give up on me ACE 😀 .
FYI, when I try distance No. 1. The corners seems to focus better than No. 2. Allthough still blurry. But not as blurr as with No.2.
Oh yea, I've published my result in : http://dewil.thefreebizhost.com.
Come n check it our people. The language is in Indonesia. But picture speaks a thousand word right....😀
1. 15mm to BF 20mm to FF.
2. 20mm to BF 20mm to FF.
3. 20mm to BF 25,20,25,40mm to FF.
(BF = Bottom Fresnel, FF = Field Fresnel).
Still a no go. Please don't give up on me ACE 😀 .
FYI, when I try distance No. 1. The corners seems to focus better than No. 2. Allthough still blurry. But not as blurr as with No.2.
Oh yea, I've published my result in : http://dewil.thefreebizhost.com.
Come n check it our people. The language is in Indonesia. But picture speaks a thousand word right....😀
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