DIY anamorphic lens

[Mark Techer]

I see what you mean about the surfboard resin! Good luck with the casting resin.

Thanks I bought another Kg tin today and filled the mold that I prepared yesterday. I think I had too much hardener(again ), as the resin itself cracked. I used the hot box and kept the prism at over 25degC, but I think because the "thick" end heats right up, I need to back down the cat below half a percent/volume...

These photos look a bit yellow due to poor light. I used the "landscape" setting on the camera tonight and the GF then informs me that it will blur the back ground (not the best thing to show clarity of the resin but as you can see, this resin is clear. These peices look like glass, and are as brittle as glass...



I'm annoyed that the prism cracked. This might just have been the best pour to date - 100% bubble free - no vacuum chamber required...Oh well, at least I recovered my glass so I can make another mold

In your post 515 you discuss an optics specialist (from OPSM) who makes prisms out of CR39. Did you, or are you able to, get CR39 from him?

No I never got back on to that guy. He went on holidays for five weeks, and when I tried to call, I could not seem to get back in touch...

What are the prism angles that Prismasonic use and what are they made of?

I have never had the oppertunity to actually measure the angles, but they look thinner than 10degree, more closer to 5 or 7 degree...They are made from Optic Glass (probably BK7)...

Mark

[Steve Scherrer]

Mark--as you have commented that the material is very "glass" like, it got me thinking--why not use glass? A secretary at my work has a couple of these glass blocks on her desk that are crystal clear, and they have embedded inside an image that has been lasered into the block to form a 3-d pattern.

The one has a flower inside, and is about 4 inches tall by 2 inches wide. I turn it over, and the price tag on the bottom indicates that it was purchased from an "everything under $1" store (we have these here in the States, where everything in the store is $1 or less.

This astounded me--considering how crystal clear the glass was, and how smooth the edges were. And she couldn't have paid more than $1 for this! So how hard would it be to obtain a couple of glass wedges? Granted, they would have to be bigger, but they can't be too expensive, right?

I did some searching, and found this from a store, where you can have words etched into glass forms:

http://www.thingsremembered.com/weba..._564481_-1_537

And while this is expensive, I have to think that there has got to be a way to get these things made, and pretty cheaply, without the resin problems you are trying to solve (although that's a pretty cool solution, as well).

Here's another link:

http://www.crystalgiftsengraved.com/standupawards.html

and an image from that page:



The largest wedge has dimensions: 6in. x 7.5in. x 1.5in.

Just thought I'd pass these thoughts along...

[fisher]

Hi Mark,

Those look great (if they had stayed in one peice!).

Did you use a release agent with the glass?

What brand of casting resin are you using? I didn't notice any heating at all during curing. It may be that the hot box is causing the cure to happen too quickly and creating stress as the thickness changes along the prism.

have never had the oppertunity to actually measure the angles, but they look thinner than 10degree, more closer to 5 or 7 degree...They are made from Optic Glass (probably BK7)...

That's interesting. Glass has a lower refractive index than casting resin (BK7 is around 1.5 vs 1.5 to 1.7 for casting resins). I haven't researched this but I assumed that the higher the refractive index, the thinner the prism.

How many prisms in the Prismasonic (were they achromatic pairs), and did the angles look about the same as you have used before (by this I mean the positions of the prisms relative to each other)?

Hello Steve, this would be a great idea if we could find an existing product line. From what I have read, one-off is very expensive.

Greg

[Mark Techer]

Steve,

If you can find those prisms with NO marking inside or out, your set. The clarity of that product is about as good as you can get. I have tried a few manufactures, and they want huge $$$ for "one offs".

The largest wedge has dimensions: 6in. x 7.5in. x 1.5in.

I also need the large prism to be 8 x 6" (7.5" is close enough ) and most of that stuff is 4" max, so both your attachment and the first link looks promising. Good luck with that and keep us updated...

Fisher,

No release agent was used. The resin contracted about 3mm, so came away from the glass without incident. The sides are (where there no cracks) smooth as the glass they were cast from.

Fibre Glass Internation is the brand I have been using. Their "Clear Casting and Embedding" resin is affordable ($A22/Ltr) and works really (as soon as I fix the thermal issues) well.

Last pour (without the hot box), the air temp on the out side was too low compared to the heat from with in. The results were not positive and as a result, both the resin and glass cracked.

I simply used two "flood lamps" and monitored the temp with a thermometer shutting them off when the temp got too high.

I really just think it was a case of TOO MUCH hardender...

How many prisms in the Prismasonic (were they achromatic pairs), and did the angles look about the same as you have used before (by this I mean the positions of the prisms relative to each other)?

They make two types - 2 and 4 prism lenes. The 4 prism lens (cost twice as much) has the two sets of achromatic pairs virtually eliminating CA...

As for the angles, what I have noticed between my 30 degree water prisms and the few 10 degree resin casts (that did work) is that the front angle (the part of the prism that faces the screen) seems to remain close, hence why I don't believe that 20;26 and or 30 degrees were even necessary. Whilst I don't think they are exactly the same, they are close. That same goes for the rear prism (facing the projector)...

Mark

[Steve Scherrer]

For the optical wedges that I found--just curious, how much money is too much? The cheapest I found them is US$36 for the smallest (4x6), $50 for the medium (5x7) and $66 for the large (6x7.5).

I called the one company, and although they are out of stock, can provide these with no markings whatsoever. I asked how clear they were, and the woman I spoke to said they had no visible markings, striations, colors, or any impurities in the crystal.

I think I will order a couple, and see how they come out. If they are no good, well I'll have wasted a bit of money--but if they work, I could get my horizontal expansion lens I have been itching for...

I was thinking of ordering the small one and the medium one. They seem pretty thin, and if they are pretty close to the projector, they wouldn't need to be that big, would they?

[Mark Techer]

Steve,

If they have no markings, etching or engraving, buy them! Buy them NOW for those prices!!! You need at least one 4" x 6" (rear prism) and one 6" x 7.5" (front prism). Or you could use 2 of the same size and build a reversable lens - HE one way and VC when turned and rotated, but at a minium you would need the sizes I have listed above or maybe replace the 4 x 6 with the 5 x 7...

It will cost you $102 with a max of $204 (+P&H and some MDF) and you will have your HE lens for a fraction of the price of a commercial equivalent...I've spent well over 5 times that just getting this far...

Do a "paper test" outlined in the beginning few pages of this thread to confirm your sizes. Remember, shorter throws need larger prisms and you want (need) so room to move so don't just go for the smaller prism if it look OK on paper, as the front prism has to be set at quite a steep angle, so the light will be wide there...

You need two of each if you want to build a 4 prism lens.

Also can you PLEASE find out how much P&H would be to Australia, becuase I want a set, and I sure that I can find few others that want them too...

I used the links and didn't even get a response to email inquiries, so if you can source them, then NO they are not too much...

Remeber I got a quote for optic prisms and it came back at $10.5K for 4 prisms...

Mark

[fisher]

Hi Mark,

How about this?



They are 170mm x 140mm and $ 88 AUD from Evright in Adelaide. See:

http://www.evright.com/showproduct.asp?P=CB8A

I have tried to contact the NZ agent but got voicemail.

Greg

[Mark Techer]

YOUR KIDDING ME!!! Can you please send me the contacts?

Mark

[fisher]

http://www.evright.com/contact.asp

Email: sales@evright.com
Head Office (Australia)

208 Gouger Street
Adelaide, South Australia, 5000
Phone: +61-8-8231-2746
Fax: +61-8-8221-6355
ABN 88 365 825 639

[Mark Techer]

Thanks Fisher.

I used the link and found a contact number, called them and ordered a pair.

They should be here next week

If they work out as a 2 prism lens, I will order another set and build a 4 prism lens. The only problem is that they come in one size only (not really a problem for me) so it will effect the overall size of the lens...


We have to be aware that these are not BK7, but a crystal, so it will be interesting to see (yes pun intended) how they look

Getting exciting now - stay tunned...

Mark