135mm long-throw lense kit from diylabs

[Me2!]

LOL, ive got a few tricks up my sleeve, including a new light engine that recycles lost light, ill try that in a few days .

Kool!

I tried to make 1 with a polarizing reflector and 1/4 wave retarder plate in front of a first surface mirror.

Idea was the light of the right polarity goes through to the LCD. Light with wrong polarity is reflected, turned 90deg, hits the mirror, turned 90deg and goes to the LCD with the right polarity!

Great!

Only problem is the 1/4 wave retarders only work at specific light frequencies so you need 1 for red, 1 for blue , 1 for green which is damned expensive. Also all these layers absorb a bit so you dont gain that much. I torpedo'd it.

I'd love to hear your solution.

[Hezz]

Guys,

I hate to admit it but one thing you should be aware of and Rox is right about this, is that the laser test will not give you the correct FOV. It will only tell you the maximum angle that the lens system can pass light through it.

The problem with the laser method is that it is only one wavelength of light. Or at least a very narrow band. The FOV is the angle where at least three critical light wavelengths for daylight have been corrected for. The FOV is where the correction has been made to a designed standard where the spot sizes of these three wavelengths are sufficiently small and aligned to be considered acceptable performance for the intended application.

The lens will still image to a lesser degree outside of the FOV.

Now it would not surprise me based on the cost of this lens that it only has a 24 total angle FOV like Rox claims the manufacturer has said. The lens was probably cobbled together from existing stock lenses to make it cheap. This would explain why the edge blurriness is a problem and the only way to deal with it would be to reduce the corner to corner distance of the LCD by using a 4:3 aspect ratio or smaller LCD.

That being said we must as Guy said put things into perspective. THis is the best lens for a 17 inch LCD for a low cost that we have at the present time. And we in all likelihood will have to get by with it until someone can get a manufacturer to have a fully optimized large format triplet made. This will cost a lot more. The last quote that someone got out of India was about 500 - 600 USD per lens for at least 100 quantity.

Rox,

If you use a high quality 10 or 12 inch LCD with this lens you should have a lot less edge problems.

I would rather live with the edge problems until I can get a better lens either by making it by hand or something else.

Hezz

[Rox]

Originally posted by Hezz
The problem with the laser method is that it is only one wavelength of light. Or at least a very narrow band. The FOV is the angle where at least three critical light wavelengths for daylight have been corrected for. The FOV is where the correction has been made to a designed standard where the spot sizes of these three wavelengths are sufficiently small and aligned to be considered acceptable performance for the intended application.

Rox,

If you use a high quality 10 or 12 inch LCD with this lens you should have a lot less edge problems.

I would rather live with the edge problems until I can get a better lens either by making it by hand or something else.

Hezz

THANKS!!!!! (I really thank that at least one of the menbers here agree in some litle point with me) thanks for this hezz.

I agree with you. I think tis lens is a good choice for our setups yet. But WE HAVE TO ASSUME SOME LIMITATIONS THAT MOSTLY CAME FROM THE TRIPLET ITSFELF, NOT FROM THE FIELD FRESNLELL AS WOULD BE THE UNFOCUSED CORNERS AND A MAXIMAL THROW SO THIS DISTORTIONS KEEP UNDER ACCEPTABLE VALUES).

I have been well maneredly kicked from a popular forum right now (my rights have been suddenly dropped to a point where i can´t even post replys, this is a well maered way for me :d)

Thisis right now the only forum where the information can´t be delted if the owner doesn´t like it. Actually I understand that if someone sells an item, doesn´t like to read it isn´t the correct item for the setup on his own forum. But I don´t like people being cheated. I really started myinvestigation for me, but then thought this information is very usefull for the comunity.

just let me tell you that i would say 80 triplet would do similar work with 17" or even better than 135 triplet. Thats because the fov on the 80 triplet is much larger than the 135's. (but the bad side of the 80's is the aperture, this is obyously better on the 135)


Finally let me tell you that it was me the most disgusted person when found this len's field angle.

anyway my challenge is open yet for you that try a setup with 135.
135 triplet & 15" TFT

I really thank you verymuch hezz. Have a good day.

[Rox]

now here comes the one millon question;

we have told to 3dlens our ideal fresnell lens. This lens was bassed on 135 triplet and a 100" image. A thing that it has not been checked/demostrated yet. Do we agree with this setup now? mean is the 550 fresnell our ideal fresnell lens?

this was a present from the 3dlens owner, and i start thinking we did things too fast. Please what do you think about?

[Hezz]

ROX,

Something you should know about the 80 mm lens. I had that lens and tested it and even though it has claimed wider FOV it does not have as good an image as the 135 mm with a 15 inch test image and given the same light illumination.

Meaning that it is designed to an even lower standard of resolution.

But in the end both lenses will work and what you should really be thinking about is where your projector will be placed and how big the image is. This will determine what focal length lens that you need.

For me the 327 mm FL will not work as I need 450 - 500 mm FL.

Hezz

[charlie10]

I tried to make 1 with a polarizing reflector and 1/4 wave retarder plate in front of a first surface mirror.

Idea was the light of the right polarity goes through to the LCD. Light with wrong polarity is reflected, turned 90deg, hits the mirror, turned 90deg and goes to the LCD with the right polarity!

Great!

Only problem is the 1/4 wave retarders only work at specific light frequencies so you need 1 for red, 1 for blue , 1 for green which is damned expensive. Also all these layers absorb a bit so you dont gain that much. I torpedo'd it.

I'd love to hear your solution.

Light recycling: slightly off-topic, but I haven't seen it discussed recently. I'm very happy to since I'm in the middle of tinkering with this. I've obtained a few 3M Vikuiti film samples (DRPF, DBEF), unfortunately all are "diffuse" since that's appropriate for wide-angle LCD backlights. Do they have one that's totally clear / non-diffuse? I guess I should ask my contact there, but wondering if anyone here had experience.

Also obtained a quarter-wave retarder sample. Yes there is a peak wavelength, my sample is 440nm but I think it would still do an ok job of the reds and blues? I'm having a hard time lining up all the fast axes though! I barely even know what a fast axis is. Is there a good thread to discuss this on? I'd love to hear more about your results me2.

c

[Rox]

Originally posted by Hezz
ROX,

But in the end both lenses will work and what you should really be thinking about is where your projector will be placed and how big the image is. This will determine what focal length lens that you need

yes i agree that image size and throw is the most important spec to check in our designs. But we shouldn´t forget about the field angle like have been done untill now. this is the next most important thing for me.

Lets say i try to do a projector with 15" and 80mm slide projector lens. I work out the throw, image size.... and everything looks like it would work. The main problem if i do it would be the field angle from the triplet would be just projecting a 3" central image of my 15" lcd. Thats becaouse i didn´t take care of the field angle.

[jcbklyny]

and i start thinking we did things too fast. Please what do you think about?

I think you should build a projector first.

[Rox]

it is you the first one who told me there are limitations with the throw with this lens.

And it is you as well te one that told me you got the triplet at 52cm from the lcd. If we add 20mm gap and say triplet optical center is at 6cm fartcer then you would use 2+52+6=600mm focal field. Don´t you think the 550 ideal is precipitated?

[Me2!]

Also obtained a quarter-wave retarder sample. Yes there is a peak wavelength, my sample is 440nm but I think it would still do an ok job of the reds and blues? I'm having a hard time lining up all the fast axes though! I barely even know what a fast axis is. Is there a good thread to discuss this on? I'd love to hear more about your results me2.

The plate I got was for a red scanning laser. It was designed for ~700nm. Yes, everything goes a mild pink.

Yours might work in blue. 440nm is in the purple. Not sure why they gave you a sample for that region. Unless you mean 440labda? That would be red. Usually these things are fairly specific to the wavelength. YOu might have the best source because their stuff is designed for LCDs and might have multi-layered coatings already in. Did it come in multi sheets? I'll have to check out thei stuff. Let me know how yours turns out