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Synthetic holograms with a cnc mill

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  • #31
    That isn't how it works. The entire length of the arc is required, at least most of it. The image from any particular angle of view is produced by the addition of the reflections from each portion of each arc that is correctly situated to be visible from the view point. As the viewpoint changes so does the portion of the arc that is postioned to produce the reflection.

    With some careful calculation as to angle of view it should be possible to produce an image that is only visible from a very specific direction. This is also consistent with the properties of holographic lenses.

    [added]

    In the case of the exit sign above, if I reduced the "viewport" to an area smaller than the image then the effect would be to see only a portion of the image as if seen through a hole. As your point of view changed you would see a different portion of the image, again the same as a regular hologram.
    Last edited by Evan; 01-16-2008, 11:06 AM.
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    • #32
      Ah - I see. Not at all like a static interference (moiré) pattern at all then. That makes it even more interesting.

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      • #33
        Originally posted by dp
        Ah - I see. Not at all like a static interference (moiré) pattern at all then.
        Apparently when Bill Beaty first published this article, a bunch of folks wrote in pointing out that his "abrasion holograms" didn't function strictly by optical interference, and were therefore not holograms.

        So Bill has a whole page dedicated to that discussion:

        Not Really Holograms?

        First of all, be aware that a diffraction grating does not function exclusively by optical interference. In addition to acting as diffractors, all diffraction gratings are also arrays of parallel line-scatterers. Because the line-scatterers (the diffraction fringes) are spaced equally, only light scattered from certain angles is reinforced while light from all other angles is eliminated. But because the fringes are line-scatters, their orientation determines the angle of deflection of the diffracted beams. If it did not, then gratings would diffract light into a cone rather than into a pair of 1st-order beams. (This of course is obvious, but it's so obvious that we might overlook it!)

        BUT ARE THEY HOLOGRAMS?

        The answer is a matter of opinion. Some people don't regard Rainbow holograms as true holograms either. These "scratch holograms" are even further away from the original off-axis holographic technique of the 1960s. Yet they do include the arrays of line-scatterers which all holograms exhibit. And they do rely on coherent reflection of an illumination beam, and so they absolutely require point-source illumination, and cannot be used with extended light sources. Use of extended-source illuminators causes severe depth-blurring in every sort of holographic recording. Simply because "scratch-holos" suffer from the same unique limitations as conventional holograms, that alone is enough to declare them to be truly holographic.
        "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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        • #34
          BTW, my server has jumped by 4 gigs over normal for the last few days. Apparently some people are not just following the links but also cruising around this site. I haven't analyzed the logs yet but they will tell me if that is so. I'm not concerned about bandwidth allowance as I have a limit of 100 gigs per month but the server load has the potential to have an impact on the commercial web pages I host.
          Free software for calculating bolt circles and similar: Click Here

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          • #35
            It's a great topic, Evan.









            All your bandwidth are belong to us!

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            • #36
              Holy Holograms!

              Originally posted by tony ennis
              It's a great topic, Evan.
              It could be the greatest topic conceivable.

              According to this, we may all be part of a cosmic hologram. From http://www.newscientist.com/article/...ss&nsref=space
              ... we would have directly observed the quantum of time," says Hogan. "It's the smallest possible interval of time - the Planck length divided by the speed of light."

              More importantly, confirming the holographic principle would be a big help to researchers trying to unite quantum mechanics and Einstein's theory of gravity. Today the most popular approach to quantum gravity is string theory, which researchers hope could describe happenings in the universe at the most fundamental level. But it is not the only show in town. "Holographic space-time is used in certain approaches to quantising gravity that have a strong connection to string theory," says Cramer. "Consequently, some quantum gravity theories might be falsified and others reinforced."


              New experiments are probably now being planned.
              Last edited by aostling; 01-15-2009, 10:13 PM.
              Allan Ostling

              Phoenix, Arizona

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              • #37
                I don't believe that the mathematics for any of the grand unification theories is well enough developed to make any predictions that can be experimentally tested. So far as I know to now it is no more than an elaborate thought experiment. This is particularly true of string theory and various poly-dimensional versions of TOE-theories.
                Free software for calculating bolt circles and similar: Click Here

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                • #38
                  WTF where is teh picture?

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                  • #39
                    Hogan did predict a certain effect, which might have been detected. But ..

                    No one - including Hogan - is yet claiming that GEO600 has found evidence that we live in a holographic universe. It is far too soon to say. "There could still be a mundane source of the noise," Hogan admits.

                    GEO600 is a gravity wave detector. In 1973 (when I was living in New Zealand) a mathematician I knew told me that gravity wave astronomy would become a reality in our lifetime. I wonder if he was right.
                    Allan Ostling

                    Phoenix, Arizona

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