Search found 405 matches

by Din
Fri Nov 24, 2023 4:17 pm
Forum: Off Topic
Topic: Whatever Became of Holography?
Replies: 19
Views: 40954

Re: Whatever Became of Holography?

So, do you actually expect ALL of us to buy this book to follow your arguments? Are you then incapable of actually giving just a single equation, quoting a single paragraph?. Perhaps, since your author references Kogelnik, you can give us the equation that your author quotes? We ALL need to buy this...
by Din
Fri Nov 24, 2023 3:05 pm
Forum: Off Topic
Topic: Whatever Became of Holography?
Replies: 19
Views: 40954

Re: Whatever Became of Holography?

Oh, wait! I think I see your point. If an edge-lit hologram is recorded with TM polarisation, then r.s = 0, where r and s are the vector representations of the reference and signal waves, because r and s have an angular separation of π/2. Since we have M = k[ r.s (cos(phase))], the modulation vanish...
by Din
Fri Nov 24, 2023 2:39 pm
Forum: Off Topic
Topic: Whatever Became of Holography?
Replies: 19
Views: 40954

Re: Whatever Became of Holography?

Then quote those equations. How about you get the book? Normally, in an environment of physics/ mathematics and engineering, one does not quote a reference by insisting that one buys a book just for one section. Normally, in an environment of physics/mathematics and engineering, it should be possib...
by Din
Fri Nov 24, 2023 1:18 pm
Forum: Off Topic
Topic: Whatever Became of Holography?
Replies: 19
Views: 40954

Re: Whatever Became of Holography?

Then quote those equations. Also, interpret those equations. If you look at Hans Bjelkhagen's expression for the diffraction efficiency for a reflection hologram, you'll see it has no variable for polarisation. I can't attach the appropriate page because I'm told: "Sorry, the board attachment q...
by Din
Fri Nov 24, 2023 10:35 am
Forum: Off Topic
Topic: Whatever Became of Holography?
Replies: 19
Views: 40954

Re: Whatever Became of Holography?

When the reference and object beams are in air, the replay polarization dependance is very small, and can easily be disregarded by inclusion with scatter, absorption and Fresnel reflections (which are seldom measured). When making "edge-lit" holograms, or HOEs where at least one of the be...
by Din
Fri Nov 24, 2023 10:16 am
Forum: Off Topic
Topic: Whatever Became of Holography?
Replies: 19
Views: 40954

Re: Whatever Became of Holography?

This is from R.R.A. Syms "Practical Volume Holography" (Oxford Engineering Scientific Series), Oxford Science Publications, 1990, page 184: "Even for weakly modulated gratings, coupled wave theory predicts a considerable difference in diffraction efficiency between the two possible r...
by Din
Thu Nov 02, 2023 12:39 pm
Forum: Off Topic
Topic: Whatever Became of Holography?
Replies: 19
Views: 40954

Re: Whatever Became of Holography?

Unfortunately a sub-group of display holographers has swallowed the idea of picture meaning an actual picture of a cat, for example, and get pretty nasty when the idea of 'picture' in the scientific sense of information is broought forward. I don't know if you're referring to me or not, Din, but I'...
by Din
Wed Nov 01, 2023 12:01 pm
Forum: Off Topic
Topic: Whatever Became of Holography?
Replies: 19
Views: 40954

Re: Whatever Became of Holography?

I have always felt that "holography" should only be considered a method (or tool, component, etc.) for a much more general purpose. When a person sees a hologram, and says "what is it?" the answer should be ___________ (fill in the blank, something other than "it's a hologr...
by Din
Mon Oct 30, 2023 12:15 pm
Forum: DCG
Topic: Angular Bandwidth in DCG
Replies: 10
Views: 14826

Re: Angular Bandwidth in DCG

Joe, You need to be careful drawing conclusions on angular bandwidth as it applies to the kind of holograms you make, as opposed to the kind of hologram used in their paper. Firstly, they're using an old method of making dcg plates by taking a silver halide plate (Kodak 649F), fixing out the silver ...
by Din
Tue Oct 24, 2023 1:01 pm
Forum: Off Topic
Topic: Whatever Became of Holography?
Replies: 19
Views: 40954

Whatever Became of Holography?

https://www.americanscientist.org/article/whatever-became-of-holography An article in American Scientist by Sean Johnston; some of you may know him as having received a grant to write the history of holography, he was a presence in a lot of the conferences about 10 years ago ( https://global.oup.com...