Hi charlie10,
[Don't mean to hijack this thread, Ace can put us in his thread when ready.]
I just checked out the vituiti films. They seem to be designed for capturing more off angle light (not from a projector like source). This is different from wave rotation where the orientation is rotated. I was wondering how they would do it for a wide spectrum and it seems they dont - unless i missed something.
I hope im wrong becasue we would have a source for recycling light. My guess is this will just fuss out your image?
Let me know.
[Don't mean to hijack this thread, Ace can put us in his thread when ready.]
I just checked out the vituiti films. They seem to be designed for capturing more off angle light (not from a projector like source). This is different from wave rotation where the orientation is rotated. I was wondering how they would do it for a wide spectrum and it seems they dont - unless i missed something.
I hope im wrong becasue we would have a source for recycling light. My guess is this will just fuss out your image?
Let me know.
Rox,
One of the hardest aspects of this DIY projector project is learning to accept compromise. The fact is that there are no inexpensive high end lenses for larger LCD's in longer 450 - 550 FL. Only OHP lenses of varying quality some of which work quite well.
The only ideal lens/LCD combination I am aware of is the 240 mm FL copy lens that ACE used with his 7 inch LCD.
This is a high quality lens that seems to work really well with that size of LCD but then you have limited resolution due to smaller LCD size.
IF you search the surplus lens sources you may be able to find a large copy lens but they usually have a shorter FL. One possible place is a large format photography lens. They have them on e-bay and most of the reasonably priced ones are in europe.
Here is onethat might be good to bid on:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=30076&item=7510309214&rd=1
Hezz
One of the hardest aspects of this DIY projector project is learning to accept compromise. The fact is that there are no inexpensive high end lenses for larger LCD's in longer 450 - 550 FL. Only OHP lenses of varying quality some of which work quite well.
The only ideal lens/LCD combination I am aware of is the 240 mm FL copy lens that ACE used with his 7 inch LCD.
This is a high quality lens that seems to work really well with that size of LCD but then you have limited resolution due to smaller LCD size.
IF you search the surplus lens sources you may be able to find a large copy lens but they usually have a shorter FL. One possible place is a large format photography lens. They have them on e-bay and most of the reasonably priced ones are in europe.
Here is onethat might be good to bid on:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=30076&item=7510309214&rd=1
Hezz
Nice lens, but...
It's only about 47 mm wide, so you would have to use matching focal length fresnels to get a small enough arc image.
But the description does say it can cover 11" by 14" film, so the FOV is terrific. (Standard 15" LCDs are only 9" by 12".)
It's only about 47 mm wide, so you would have to use matching focal length fresnels to get a small enough arc image.
But the description does say it can cover 11" by 14" film, so the FOV is terrific. (Standard 15" LCDs are only 9" by 12".)
Guy,
Ya there are some issues with this lens. I think the real thing would be matching the fresnel into it's reduced aperture. OF course you could take apart the lens and remove the shutter but keeping the fresnel cone within the shutter aperture would ensure the highest quality imaging.
Hezz
Ya there are some issues with this lens. I think the real thing would be matching the fresnel into it's reduced aperture. OF course you could take apart the lens and remove the shutter but keeping the fresnel cone within the shutter aperture would ensure the highest quality imaging.
Hezz
Yup prolly should be in a separate thread.
So... my mistake earlier, my retarder sheet is 10 mil quarter wave at 560nm. Not 440nm.
The other day, I managed to disassemble a 1"x2" piece of my Vikuiti 45deg. DBEF sample and get access to a film inside, which I believe is simple RPF. It came sandwiched between two diffuser sheets, which I basically tore off (not easy). There was alot of damage and stray adhesive, but a couple of spots of somewhat clean usable material.
I tested this with both a red laser (level) and a narrow beam of halogen light, shining through the lens of an old pair of polarized sunglasses (the "LCD"), and showing up as a dot on a piece of white paper (the "screen"). My goal was to see if I could increase the brightness of the dot by using the RPF.
Testing with the laser (polarized source), it seemed to do a great job of reflecting the "s" polarized light and transmitting the "p" light, without absorbing much or sending much of it off-axis. If I twisted the sample at 45 degrees to my laser level, it behaved like a clear piece of plastic and I could barely see a shadow as I moved it between my source and screen. There was some reflection. When I then oriented it at 135 degrees, the dot on my screen became very dim and the reflection became very bright. This seemed most promising!
I then drilled a 1/16" hole in a small utility mirror (not FS) and shone the laser through that, to achieve reflection without a steep angle. Using this setup, I figured out how to best orient the "fast axis" of the retarder with respect to the RPF.
I then moved to a white unpolarized source (35W halogen), using a couple of irises to make it into a tight "beam". Shining this through the perforated mirror and bouncing it off the retarder+RPF sandwich, I was able to get a second splotch of light to show up on the screen. After many nudges and tweaks, I got the recycled light to seem about 35% as bright as the unrecycled dot. Again very promising! 🙂
However, the recycled light had a definite greenish-blue color cast, at least compared to the yellowish unrecycled halogen light. This might have been due to the RPF+retarder having a peak efficiency at 560nm, or simply to the glass in the cheapie utility mirror being green? I also noticed vertical dark lines forming shadows on the screen; I think my light source was close enough to being a point, that I saw an image of the internal structure of the RPF film.
I used my camera in fixed-exposure mode to take pictures of the results. I simply removed the QWR+RPF sandwich to get a before-and-after. Well... I wish I could say it became twice as bright, but I that was not the case.
According to the camera, it turned out about as bright, but not brighter. The various layers definitely absorb alot, and I did see alot of stray reflections etc.On the bright side 🙄 , the basic behavior of the film is good. Unlike the BEF it doesn't sent the light off at 45degree angles. I believe with a large-aperature lightsource eg. MH + reflector it would behave quite well, without stray reflections. The films can be placed in a sandwich right before the LCD, reducing heat / UV concerns. The usual box design including a polished steel reflector (IKEA / Norpro / specular metal) and a heat shield would probably not require any box redesign, just stick the films in.
The pricing quoted to me was about $50 per sheet of QWR and RPF in small quantity (6). That seems 'not worth it' but I'm guessing there are cheaper sources, and I have a feeling that recent LCDs already come with at least one of these films. I wouldn't know since I've yet to strip one myself.
That's all for now :xeyes:
Not with a focused beam on the wall it wont!!!! 😀
I didnt do the test in the manner you thought Hezz, i did it until the focussed dropped of rapidly at the side angles..........sure i could of moved the beam further round but it was out of focus hence out of the FOV.
Trev🙂
i found it difficult to xplain why but lets try once more.
If we have a laser facing the triplet lens somewhere, and we can see the laser on the wall as well (focused), then if we move the laser to other point in the lens but keeping the same place, i mean think it is a lcd pixel but is difuse in a small angle, we can point it at 2cm upper than the lens center (test1) and then 2cm downer than the lens center (test2), this way the lcd pixel is on the same place but we have 2 diferent laser beams FROM THE SAME PIXEL. So if we check the projection on the wall, the projected focused image will move a distance form test1 to test2.
I mean, if we just look to one test laser pointer, we would think it is focused and it is the field angle of the lens. But this is not true, test2 shows something is happening there. The conbined light of the two test will show a blurr image. Thats why the laser test will not give us the field angle.
in fact we don´t know how field angle is defined. Untill someobe shows it here, please do not tell me you measured it.
for instance, minotens images show blurr corners. Would anybody say where ends the fov? we cant do it because each one of us would say a different critical point. Anyway, he thinks the image is good enough for him, thats what really cares.
If we have a laser facing the triplet lens somewhere, and we can see the laser on the wall as well (focused), then if we move the laser to other point in the lens but keeping the same place, i mean think it is a lcd pixel but is difuse in a small angle, we can point it at 2cm upper than the lens center (test1) and then 2cm downer than the lens center (test2), this way the lcd pixel is on the same place but we have 2 diferent laser beams FROM THE SAME PIXEL. So if we check the projection on the wall, the projected focused image will move a distance form test1 to test2.
I mean, if we just look to one test laser pointer, we would think it is focused and it is the field angle of the lens. But this is not true, test2 shows something is happening there. The conbined light of the two test will show a blurr image. Thats why the laser test will not give us the field angle.
in fact we don´t know how field angle is defined. Untill someobe shows it here, please do not tell me you measured it.
for instance, minotens images show blurr corners. Would anybody say where ends the fov? we cant do it because each one of us would say a different critical point. Anyway, he thinks the image is good enough for him, thats what really cares.
One of the biggest things your missing Rox, flat projection medums vs curved.
You do know that some lenses are designed for lcd's (as in being flat) and others for crts (as in being curved)?
How do we know that this lens is designed for a flat screen? Ahh.... we dont.
Sure the FOV plays a role in a projection system, but honestly, the dim corners arent what do it the majority of the time on the lenses that are available to us. Sure, maybe on the 135mm triplet, but its quite simple, if you dont like others results, simply dont buy it, go for another.
We use conical grooved frensels for starters, this blurs the light on the edges of the image, how to fix this? get an aspherical frensel. Thats one reason for you and a fix. The others are wrong condenser, poor reflector or the FOV, but what i will say is that the majority of the time, its the conical grooved frensels. Another reason is the way we do things here, as i told you before a few times now project in paralle, not in a cone manner, thats one of our biggest issues with poor imaging.
I made up a test bed here, i had 6 sets of frensels and 3 projection lenses, all projection lenses projected EXACTLY the SAME on each set of frensel, and all was at different focal lengths. This was also conducted on a 7inch lcd so no FOV problem here!!!!
The result, slightly dim corners, why? the frensels are conical grooved, + then you have distortions at different wavelengths and no matter what system you build with an lcd 2inches and up, and you will always have a hot spot with a condenser. The center of a lens is more powerful then its outer, flat or curved, thats a well known fact, add 2 or 3 of these together and you have a problem.
If you realy want a projector that perfect Rox, buy one, cos in the world of diy to make a perfect projector (and it still wont be) it will cost you a fortune. You realy think pro projectors are that perfect? Go and see one going and come back and tell me the limitations of physics 🙂.
Trev🙂
You do know that some lenses are designed for lcd's (as in being flat) and others for crts (as in being curved)?
How do we know that this lens is designed for a flat screen? Ahh.... we dont.
Sure the FOV plays a role in a projection system, but honestly, the dim corners arent what do it the majority of the time on the lenses that are available to us. Sure, maybe on the 135mm triplet, but its quite simple, if you dont like others results, simply dont buy it, go for another.
We use conical grooved frensels for starters, this blurs the light on the edges of the image, how to fix this? get an aspherical frensel. Thats one reason for you and a fix. The others are wrong condenser, poor reflector or the FOV, but what i will say is that the majority of the time, its the conical grooved frensels. Another reason is the way we do things here, as i told you before a few times now project in paralle, not in a cone manner, thats one of our biggest issues with poor imaging.
I made up a test bed here, i had 6 sets of frensels and 3 projection lenses, all projection lenses projected EXACTLY the SAME on each set of frensel, and all was at different focal lengths. This was also conducted on a 7inch lcd so no FOV problem here!!!!
The result, slightly dim corners, why? the frensels are conical grooved, + then you have distortions at different wavelengths and no matter what system you build with an lcd 2inches and up, and you will always have a hot spot with a condenser. The center of a lens is more powerful then its outer, flat or curved, thats a well known fact, add 2 or 3 of these together and you have a problem.
If you realy want a projector that perfect Rox, buy one, cos in the world of diy to make a perfect projector (and it still wont be) it will cost you a fortune. You realy think pro projectors are that perfect? Go and see one going and come back and tell me the limitations of physics 🙂.
Trev🙂
here is a confusion;
i don´t want a pro projector. I love playing with this stuff and found it very entertaining. But there are some points that people say that i don´t think is true or something exagerated at least.
The fiel angle of a projection lens is as helpfull as the focal lenght for me. When i started to design my projector, i tryed different triplets focal... and worked out the one i would like to have (for my desired image size and the throw availlable where i want to place it) but then thought; what would be the field angle of this lens? would it be sufficent for my setup? and started to find this information. Well incredibly no body knew it. Two month later i got the spec and get supprised. Then i thought it would not work for my setup. But there is people havving succes somehow, well, i asked them for photos (i started a thread as well where i challenge them to post results, but no replys yet) i have contacted with people but they only tell me it works, no photos as JCB told me. Then the informaiton provided by them is confussing, things do not macth at all (astaples for instance says that 5,5" bulb placemnt betewwn rear fresnell and bulb works fine with 17" lcd; thats not posible) I don´t understand what is happening there. Maybe theyonly think on bussines? i don´t like to be cheated, i guess nobody does.
JCB has a store, and i understand that if the image is limited somehow, he doesn´t want to be known. olthought he es the only one that told me there are some limitations with this lens, isn´t very clear anyway.... told me all nformation is at his page. well i don´t like to pay for forums, i think it is not the idea of sharing comunity.
Well, minoten has recently posted some pictures. the image is fine but it is not corner to corner focus, as claimeb by some people. I think my thead challenging people isn´t going to be too large 😀
I think the design on the paper can be very accurate, if you design it very carefully taking on acount all as posible elemnts, i don´t undrestand why shouldnt it be close to reallity (in fact hats the functionallity of the specs, they are defined in by some parameters so we can use them on paper, don´t you think so?).
I have been told that 1/F=1/D + 1/T does not follow the reallity when concerned about the lcd-triplet-projection, well my test on this are exactly as espected. Maybe the one who told me isn´t as accurate as me on this.
Finally let me tell you i plan on a design as A STARTING POINT, then play with the positions +/- some cm o see if it gets worst or better.
i don´t want a pro projector. I love playing with this stuff and found it very entertaining. But there are some points that people say that i don´t think is true or something exagerated at least.
The fiel angle of a projection lens is as helpfull as the focal lenght for me. When i started to design my projector, i tryed different triplets focal... and worked out the one i would like to have (for my desired image size and the throw availlable where i want to place it) but then thought; what would be the field angle of this lens? would it be sufficent for my setup? and started to find this information. Well incredibly no body knew it. Two month later i got the spec and get supprised. Then i thought it would not work for my setup. But there is people havving succes somehow, well, i asked them for photos (i started a thread as well where i challenge them to post results, but no replys yet) i have contacted with people but they only tell me it works, no photos as JCB told me. Then the informaiton provided by them is confussing, things do not macth at all (astaples for instance says that 5,5" bulb placemnt betewwn rear fresnell and bulb works fine with 17" lcd; thats not posible) I don´t understand what is happening there. Maybe theyonly think on bussines? i don´t like to be cheated, i guess nobody does.
JCB has a store, and i understand that if the image is limited somehow, he doesn´t want to be known. olthought he es the only one that told me there are some limitations with this lens, isn´t very clear anyway.... told me all nformation is at his page. well i don´t like to pay for forums, i think it is not the idea of sharing comunity.
Well, minoten has recently posted some pictures. the image is fine but it is not corner to corner focus, as claimeb by some people. I think my thead challenging people isn´t going to be too large 😀
I think the design on the paper can be very accurate, if you design it very carefully taking on acount all as posible elemnts, i don´t undrestand why shouldnt it be close to reallity (in fact hats the functionallity of the specs, they are defined in by some parameters so we can use them on paper, don´t you think so?).
I have been told that 1/F=1/D + 1/T does not follow the reallity when concerned about the lcd-triplet-projection, well my test on this are exactly as espected. Maybe the one who told me isn´t as accurate as me on this.
Finally let me tell you i plan on a design as A STARTING POINT, then play with the positions +/- some cm o see if it gets worst or better.
ACE,
Ok your explanation of the laser test makes a little more sense but I still think that it will be only an approximation of the actual full spectrum FOV. Depending on how wide a band the laser puts out the closer it will be. However the full daylight FOV wil be narrower than your laser test so it can be expected that if your laser got blurry at a certain point with full color the FOV would be somewhat narrower.
Guys,
After viewing the images that Rox asked us to view in his other thread I think that there are two different issues. Because it is obvious that the corners are darker in those pictures and yet at the same time the focus is good out to the corners.
So we have to treat focus and light level at the corners as different issues.
It is possible that this 135 mm triplet is a copy of an old design meant for old curved CRT projection. If that is the case it might be wise to check the MSN DIY TV projection forum and see if anyone is using this lens with similar problems.
Hezz
Ok your explanation of the laser test makes a little more sense but I still think that it will be only an approximation of the actual full spectrum FOV. Depending on how wide a band the laser puts out the closer it will be. However the full daylight FOV wil be narrower than your laser test so it can be expected that if your laser got blurry at a certain point with full color the FOV would be somewhat narrower.
Guys,
After viewing the images that Rox asked us to view in his other thread I think that there are two different issues. Because it is obvious that the corners are darker in those pictures and yet at the same time the focus is good out to the corners.
So we have to treat focus and light level at the corners as different issues.
It is possible that this 135 mm triplet is a copy of an old design meant for old curved CRT projection. If that is the case it might be wise to check the MSN DIY TV projection forum and see if anyone is using this lens with similar problems.
Hezz
Rox,
You better think abou this. Saying that all these people are covering up to protect sales or whatever reason is basically slander. For the guys with businesses you are accusing them of fraud.
What is your proof?
I dont think you meant it like that but that is the way it reads to everyone else. Please consider how to be constructive in your posts.
You better think abou this. Saying that all these people are covering up to protect sales or whatever reason is basically slander. For the guys with businesses you are accusing them of fraud.
What is your proof?I dont think you meant it like that but that is the way it reads to everyone else. Please consider how to be constructive in your posts.
Exactly Hezz, (good to see you btw) thats all it was, a 5 min test 🙂.
A rule i commonly follow is if you can, try to have the FOV you need half of what the lens has in its specs, i do the same with arperature, that way your know your fine and will get the best possible image out of the lens in our type of setups.
To me, large panels are more of a pain then anything, thats why i dont bother with them, 7inch is still to big to me.
Trev🙂
Everybody knows the feild of veiw that they need when they draw a plan, its upto the manufacturer or supplier to supply the specs of the lens. If you are on a budget and dont want to risk buying a lens that wont work, dont buy it.
Yep, thats typical, i dont have photos simply because id rather spend my money on others things then a cam to just show screen shots, other then that im broke from buying all of the optics ive tested over the last 2 years!!!
Last year i made over 32 setups of others designs to prove a point i was courious about. I made the setups with the exact same spacings and parts, guess what? the screen shots you see in here are not the same as reality (not all), most are brighter from having the cam over exsposed to light. Now while that was my findings, im not going to go out and say who it was who was lying, and blame the actual person, because at times cameras have CCd's more sensitive to others at different wavelengths of light, so i cant go just blaming the person.
However, weather the person lies or not, we all should still praise the work and effort they have put into their project. Weather another member makes a clone of the project and isnt happy with the results as what was seen in the pic, honestly, thats not my problem, and the truth comes out in the end.
Thats possible, but the image must be messed in reality. How can the light be going through the lcd paralelle if the source is short of the rear frensels focal? thats impossible lol and will yeald a blury fuzzy image.
A rule i follow is ALWAYS work from the light source back to the projection lens, never the otherway or it simply wont work right.
Thats right, i always work to a plan on paper, the only ajustments should only be in mm's and on the mirrors (if using them), no way cm's 😀. As you said, providing its planned out right.
Trev🙂
I have proof of a certain company in my email that i saved.......... but your right, slander and acusations do not belong in here.
People who lie and rip others off get caught out sooner or later, reputation is also a very powerful thing 🙂.
Trev🙂
I don´t tried to give bad reputation to anybody, just found some information non sense from them, also was tested by 3rd person and the expected imabe was as i predicted. (hot spot in the midle and black image on a lcd out of 3" circle at the midle, his is because the bulb placement was too close to the rear fresnell, the light was divergent on the output so only the central part was hiiting the triplet; the conbined focal of 330/330 is 6,5" so if you place the bulb at 6,5" the light would be parallel teorically, thats alredy a wrong setup cos only the 130mm circle will enter the triplet. Now if you go closer 5,5" then the light would be diverging and less area of the lcd would enter the triplet, you got it?
about the field angle, i just knew the field angle required by my setup and just wonder if the lens that are available had same or more that angle. Found a dissgusting field angle on the 135 lens case.
Sometimes, the specs of a item told by the seller aren´t full specs and its hard to find them (on ebay, you can find lot of TFT with lot of imformation from the manufacturer for instance but most of it non interesting information, you can read full page of specs but the response time could be missing for instance, then if you have luck and search the exact model number/panel number or wharever, maybe you can get to a disgusting response time (50ms), thats the reason why the seller didn´t write down with rest of imformation. I wonder if it is the same case with the 135 lens field angle.
but for me the best prove is that nobody takes the my challenge.
about the field angle, i just knew the field angle required by my setup and just wonder if the lens that are available had same or more that angle. Found a dissgusting field angle on the 135 lens case.
Sometimes, the specs of a item told by the seller aren´t full specs and its hard to find them (on ebay, you can find lot of TFT with lot of imformation from the manufacturer for instance but most of it non interesting information, you can read full page of specs but the response time could be missing for instance, then if you have luck and search the exact model number/panel number or wharever, maybe you can get to a disgusting response time (50ms), thats the reason why the seller didn´t write down with rest of imformation. I wonder if it is the same case with the 135 lens field angle.
but for me the best prove is that nobody takes the my challenge.
Hezz said:
forgot to mention, this 135 lens was oriinally designed for OPAQUE PROJECTORS.
I posted full specs on a thread somewhere.
Like i said, im sure that was not your intent and im sure the English is part of the issue.
You found they made a mistake? Found ongoing incompetence? Found they intensionaly mislead their customers? These are all very different but it is hard to tell which you mean from your post.
I also am not sure what you mean by disgusting field angle. I could guess but would i get what you really meant?
Your looking into the field angle issue on these parts has helped many with their project im sure.
Send me over the triplet, the lcd and the frensels and ill have it sorted in a day for you, im not going to spend money on a 15/17inch test bench just to see if somthing works, or to take on any chellenge Rox. Those with the gear, fair enough, but they dont have to.......
Trev🙂
As probably the top designer on the board I’m surprised you don’t have this already! I know u specialize in the 7" but still... 😉
These bits are getting expensive for me too.
Just think, someday you might have a design that will be licensed by others and your efforts will bring affordable home theatre to the masses.
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