DIGITAL 2011

[holomaker]

How did you calculate the Lens to produce a sharp image on the ground glass?

No need to calculate, I have many lens for trial and error

What's the space between DMD and ground glass?

About 45 inches

I did some experiments in this direction , too, but always had the problem to produce a sharp image on the glass.

Be sure to use a plano/convex lens with the flat side facing the DMD, and the aperture to cut off out of focus edges

How big is the picture on the screen, and what about incident angle? Do you come normal to the face of the screen?

It’s about 11”x14 “active area and yes normal

Can you describe, or even take a video how the picture on the screen looks like when you view it from the opposite side?

I will work on some photos to show

So in other words, how good does your ground glass diffuse in all directions, and what exactly did you use for your screen

The further the distance between the diffuser and the DMD the better, yes its slightly hotter when viewing normal but this can actually be adjusted to a minimum, the frosted screen was actually made by using a spray on frosted coating on regular glass

[HoloM]

Why is a Plano convex lens needed? Isn't it the same with a double convex?

Which focal length does yours have? Your picture seems to show about 4". Is that right?


46" is quite a long distance between DMD and ground glass you need a huge table. Do you fold the beam? Or how is your geometry on the table?

What is a 'spray on frosted coating ' ?



Cooll work! I like it! And thanks for sharing the information!

[Ed Wesly]

Since you guys are going through teething pains with your stereogram set ups, I invite you to check out the trials and tribulations of the School of the Art Institute of Chicago Stereogram team, circa 1997. Finally got around to posting this paper on my web site!

http://nlutie.com/ewesly/SAICPrinter.pdf

[holomaker]

Hey Ed , thanks for the great link! I appreciate the earlier trials and tribulations of these earlier days. I Guess the song is still the same, it just has some different singers now. Seriously while the principals are the same, its the new technology to be applied here, like the HD video footage and the projection system that will be different than past attempts ........

A modeling clay mounted mirror in a split beam setup...a setup where your trying to do dozens of holograms in a row, all perfect? I don't want to sound too picky but I have to ask

Yes Jeffery you are correct in your thoughts, But i have found it much easier to do mock setups using this clay. Its stable enough to hold tight for a test or two, and then if all goes well, I will find a more permanent solution. Many time ive used this clay to hold my objects/mirrors in place during 5 minuet exposures, so i know it works well !

[Jeffrey Weil]

Hello Dave,

Hey, if the clay works.....cool.

When you do go to fix it down he's an idea you might like. I sometimes take the arm from cheap mag mounts and mount them to other things.

The shutter you sold me is a good example, I have it mounted to a small alum foot. That's bolted down to the laser shelf and the shutter is on the end. Now it's an adjustable mount. You could do the same with your mirror. Just mount the mag arm up there. Easy to adjust and perfect for real exposures.

When can we see a final h2?

Jeff W

[holomaker]

Why is a Plano convex lens needed? Isn't it the same with a double convex?
by keeping the flat side of the lens facing the DMD will keep edges in better focus

Which focal length does yours have? Your picture seems to show about 4". Is that right?

its like 3" or less FL

46" is quite a long distance between DMD and ground glass you need a huge table. Do you fold the beam? Or how is your geometry on the table?

my table is 10' long and the distance is actually longer then the 46" stated

What is a 'spray on frosted coating ' ?

it's called Glass Frosting, made by Krylon. and it works Very well, you apply it in numerious coats untill you are satisfyed with the ammount of frosting needed



Cooll work! I like it! And thanks for sharing the information!

im acually ready to shoot a real master tonight if my D-19 is still good !

[Dinesh]

Why is a Plano convex lens needed? Isn't it the same with a double convex?

No, not quite. It can be shown that a plano convex lens will have less spherical aberrations than a double convex lens and will, in fact, have minimise spherical aberrations of all singlet lens shapes. There is a factor called the q factor, or shape factor, or Coddington shape factor, this is a function of the index and the radii of the two faces of the lens. You can plot q against spherical aberrations and see that the minimum of this curve occurs for the q factor corresponding to a plano convex lens.

[kaveh1000]

Why is a Plano convex lens needed? Isn't it the same with a double convex?

No, not quite. It can be shown that a plano convex lens will have less spherical aberrations than a double convex lens and will, in fact, have minimise spherical aberrations of all singlet lens shapes. There is a factor called the q factor, or shape factor, or Coddington shape factor, this is a function of the index and the radii of the two faces of the lens. You can plot q against spherical aberrations and see that the minimum of this curve occurs for the q factor corresponding to a plano convex lens.

Not quite. Best shape is biconvex but with the side facing the diverging beam almost planar. As plano-convex is much cheaper, people use that. So very close approximation to the minimum for a single lens.

[Dinesh]

Yes, true. I was answering the question of why a plano-convex is better than a biconvex, assuming commercially available, not too expensive lenses. However Kaveh's right that one face has to be almost, but not quite planar. The "best" q value is about 0.7 while a planoconvex lens has q=1. There is no one shape factor that reduces both lateral spherical aberration (LSA) and transverse spherical aberrations (TSA), since these are two separate curves. Actually, if both faces are hyperboloids, it reduces aberrations even more. But Coddington's shape fator assumes spherical faces.

At any rate, here's the page from the Melles Griot catalogue explaining about the q factor (Note that in the 2f-2f configuration, a biconvex singlet is a minimum for coma and astigmatism as well as SA):
http://www.google.com/url?sa=t&rct=j&q= ... jMxOc_BPlA

[holomaker]

Ha I was just reviewing this post as I plan on getting
“Digital image” hologram printer fired up again...

But you guys having a pissing contest about which way the lens goes,, I just had to chime in ! Im not sure which is Theoretically possible or not, but I’m already doing it ! Welcome back any responses !