Well I made a functioning zoom lens today....woohoo!
Using this lens:
http://www.surplusshed.com/pages/item/l1488.html
..with my triplet gives a scalable picture, as predicted. The triplet has to be farther out than normal. By changing the relationship of Neg lens, triplet and panel to lens distance I can scale the picture, in focus over a large area. As a matter of fact I can project an image 17' away that is 2' diagonal, and scale the image up by changing the optical arrangement.
The drawback? Barreling. Although totally in focus there is some barreling due to the neg lens. For those who don't know what barreling is, the picture bulges out on the sides and top, like an old crt TV. So my next project is correct this barreling with another optic or deduce whether another type of negative optic can help reduce this.
Using this lens:
http://www.surplusshed.com/pages/item/l1488.html
..with my triplet gives a scalable picture, as predicted. The triplet has to be farther out than normal. By changing the relationship of Neg lens, triplet and panel to lens distance I can scale the picture, in focus over a large area. As a matter of fact I can project an image 17' away that is 2' diagonal, and scale the image up by changing the optical arrangement.
The drawback? Barreling. Although totally in focus there is some barreling due to the neg lens. For those who don't know what barreling is, the picture bulges out on the sides and top, like an old crt TV. So my next project is correct this barreling with another optic or deduce whether another type of negative optic can help reduce this.
What was the positioning/orientation of the projection elements in your zoom system? And wouldn’t it be possible to use the fujinon lens in a similar optic arrangement to increase its focal length?
I'll try to get some measurements tonight, just did a quick confirmation. I haven't tried using the fuji yet, try that tonight too.
The neg lens took the place of the projection lens, the projection lens moves outward a few inches. By changing the panel to neg lens distance, and refocusing the projection lens I got zoom.
The neg lens took the place of the projection lens, the projection lens moves outward a few inches. By changing the panel to neg lens distance, and refocusing the projection lens I got zoom.
brainchild if u got barreling on the double concave try a double convex or try a concave with a lower negative power, getting one with the right focals is the pain. Also try a negative pcx curved side facing the lcd.
Trev
Trev
I would think a Plano-Concave Lens might fix the barreling being that only one side is concave and the lenses do exactly the same thing as double-concave lenses.
Actually I should have mentioned that the surplus shed listing is wrong, this is a plano/convex lens.
"The neg lens took the place of the projection lens, the projection lens moves outward a few inches. By changing the panel to neg lens distance, and refocusing the projection lens I got zoom."
Could you please make a drawing of that?
I tried messing up with the optics on a triplet but i did
not get same results.😕
Could you please make a drawing of that?
I tried messing up with the optics on a triplet but i did
not get same results.😕
I don't know if you guys saw my idea for a zoom and adjustable anamorphic lens in an earlier post. Here is the picture. The idea is that the negative lens and the cylindrical lenses can both move independently. The negative lens causes the zooming and the cylindrical compresses the vertical plane as it is moved. In this picture a large convex lens takes the place of the second fresnel which accomplishes the same task. I think the negative lens needs to be kept to moderate zooming amount so that little barrel distortion is caused. I don't know if the cylindrical lens would have to be acylindrical to work as a standard cylindrical might introduce to much abberation. It would be fun to try it out though.
Hezz
Hezz
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The diagram hezz posted isnt as complicated as it looks. It's only adding 3 lenses to the regular triplet lens assembly that most people already use.
I think your on the right track there hezz... have you tried to fool around with that lens arrangment yet?
I think your on the right track there hezz... have you tried to fool around with that lens arrangment yet?
Actually it's only adding 2 lenses because the large plano convex lens is the same as the field fresnel.
only when splitting fresnels. When both are positioned behind the lcd there is no "field" fresnel in the design. A field lens is poisitioned after the image plane.
Yes, you guys are both correct,
and the cook triplet combination takes the place of the DIY triplet that most of us have been using. The cook triplet is a higher performing lens and it is my hope that we can learn to cobble one together from readily available singlets. Or even make our own from larger diameter lenses.
Actually, athough the lens may seem complicated it may to too simple to work well enough as an adjustable anamorphic. I havn't yet got caught up financially from x mas yet so I don't have the budget to buy lenses to experiment with but I would be very interested in any of your experiences out there trying to do some experimentation.
The cylindrical miniscus lens is the one that will be hard to find and the negative zoom element needs to be such that the light entering the cylindrical miniscus is at the right angle to reduce abberations as much as possible.
One possible source for the cook triplet lens may be the large fujinon projector lenses that surplus shed was selling for 15 USD. There are probably 4 -5 lens elements in those lenses and if anyone has one they are willing to break apart to find out it might be helpful.
Hezz
and the cook triplet combination takes the place of the DIY triplet that most of us have been using. The cook triplet is a higher performing lens and it is my hope that we can learn to cobble one together from readily available singlets. Or even make our own from larger diameter lenses.
Actually, athough the lens may seem complicated it may to too simple to work well enough as an adjustable anamorphic. I havn't yet got caught up financially from x mas yet so I don't have the budget to buy lenses to experiment with but I would be very interested in any of your experiences out there trying to do some experimentation.
The cylindrical miniscus lens is the one that will be hard to find and the negative zoom element needs to be such that the light entering the cylindrical miniscus is at the right angle to reduce abberations as much as possible.
One possible source for the cook triplet lens may be the large fujinon projector lenses that surplus shed was selling for 15 USD. There are probably 4 -5 lens elements in those lenses and if anyone has one they are willing to break apart to find out it might be helpful.
Hezz
I agree. If we can find out the right combination of focal lengths we could make our own triplets or zoom type lenses that would far exceed any triplet currently being used. I would like to try and lengthen current focal lengths of the higher quality lenses available like the fujinon and such. Very much possible. But now it's a matter of finding the right surpluss optics to experiment with before investing in higher quality lenses.
I will have access to ZEMAX optical design software on a computer very soon and though I will have to study more in depth on optical design I am going to try and come up with a cook triplet design that will work from existing lenses. I may design one from available parts and one that is optimized for those who might want to try and make a lens from scratch.
I will be designing for 450 - 500 mm focal lengths as this range should accomodate both 15 and 17 inch LCD's with a throw distance that will work better for most applications.
Hezz
I will be designing for 450 - 500 mm focal lengths as this range should accomodate both 15 and 17 inch LCD's with a throw distance that will work better for most applications.
Hezz
Yes that's correct, in fact the big plano lens is oriented in this way so that the LCD can be mounted directly to the back side of the large plano thereby putting the LCD as close to the lens as possible.
The LCD is not shown in the drawing or any light engine optics prior to the LCD.
Hezz
The LCD is not shown in the drawing or any light engine optics prior to the LCD.
Hezz
lol, yes but it's not going to take the place of a fresnel lens in large panel designs. For large LCD's your not going to find a plano convex lens big enough. Zoom lenses have anywhere from 6-8 optics in them.... so you could add 3 or more to what we are currently using now for the desired effect.
You'd be hard-pressed to find one large enough for a 7" lilliput.
You'd be hard-pressed to find one large enough for a 7" lilliput.
I think we need to get some optical engineers on the forum here to work out the least expensive way to do it with the best results.... Where do we find these people. The price of SLR zoom lenses in the focal range we want is absolutely ridiculous. Can it really be that difficult. It seems like someone with the proper knowledge could surf through surplusshed and pick out the exact lenses necessary. Where are these optical engineers and how do we get them here on the forums?
thats funny! As much as that would solve all our problems It's just not gonna happen. If you speak to a few of them at optic companies they WILL help... but dont expect them to sit there and hold your hand through the process. They tend to point you in the right direction with information and formulas, all of which are already available online. It's a matter of reading through all the information, learning how each lens works by itself and then how each lens effects the other. Once you have an idea of that you can design your own lens.
We'll get it 🙂 Now that we have enough good people working on the problem it's only a matter of time.
We'll get it 🙂 Now that we have enough good people working on the problem it's only a matter of time.
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