What i am trying to figure out is how does a hologram work?. More to the point, how is it that rotating a flat holographic sticker allows the virtual object to change orientation - allowing me to see content that was not there a moment ago?

You see objects because your eyes register light that is coming from these objects. If you shift your head, your eyes will be subjected to a different "part" of reflected light waves from those objects, so you will see those objects differently -- for example you will be able to see objects that was obscured before.

Suppose that you have a techique that records completely all the light waves coming from your objects. And you also can "playback" those waves, so that they would exaclty reproduce the lightwaves from real objects. Then no one will be able to distinguish (using only one's eyes) the difference between the real objects and your "lightwave reproduction" of them. If you shift your head, your eyes will be subjected to a different "part" of "reproduced" light waves, so you will "see" those "objects" differently -- for example you will be able to "see objects" that was "obscured" before.

That is roughly what holograms do. They record the whole information about the incoming light by storing it in the interference patterns in a film. And when hologrms reflect (or, sometimes, pass through) light they reproduce exactly the lightwaves that was falling on them during recording.

...my credit card:

• has no reference beam
• is not being viewed at a 45 degree angle (meaning no interference can happen)

Well, first about interference -- 45 degree angle is not something that is necessary to see a hologram (though, some holograms can be seen from just a range of some particular angles). More importantly it is not necessary to have interfence or diffraction (diffraction is actually a more appropriate term here).

Now about reference beam. First of all -- you always need "reference beams" to see something. Light have to come from somhere to get into your eye, right? On the other hand, for basic old-style holograms it is actually necessary to use a laser beam to recreate recorded waves. But there is a more "modern" approach called volume holograms, which work in ordinary light.

What i am trying to figure out is how does a hologram work?. More to the point, how is it that rotating a flat holographic sticker allows the virtual object to change orientation - allowing me to see content that was not there a moment ago?

You see objects because your eyes register light that is coming from these objects. If you shift your head, your eyes will be subjected to a different "part" of reflected light waves from those objects, so you will see those objects differently -- for example you will be able to see objects that was obscured before.

Suppose that you have a techique that records completely all the light waves coming from your objects. And you also can "playback" those waves, so that they would exaclty reproduce the lightwaves from real objects. Then no one will be able to distinguish (using only one's eyes) the difference between the real objects and your "lightwave reproduction" of them. If you shift your head, your eyes will be subjected to a different "part" of "reproduced" light waves, so you will "see" those "objects" differently -- for example you will be able to "see objects" that was "obscured" before.

That is roughly what holograms do. They record the whole information about the incoming light by storing it in the interference patterns in a film. And when hologrms reflect (or, sometimes, pass through) light they reproduce exactly the lightwaves that was falling on them during recording.

...my credit card:

• has no reference beam
• is not being viewed at a 45 degree angle (meaning no interference can happen)

Well, first about interference. I think you misunderstand what does "interference" mean in that context. We are talking about wave interference between object wave and reference wave. The hologram records interference pattern, that is produced by wave interference of the two waves. And all that is relevant during creation of a hologram.

The interference patterns are very fine -- they are of a size of a wavelength. So there is a lot of information recorded on the hologram -- that is how all that information "fits" on one hologram.

Finally. When we reconstruct a hologram we use a reference beam, which diffracts on the recorded interference patterns and reproduces the object wave.

Now, speaking about reference beam. First of all -- you always need "reference beams" to see something. Light have to come from somwhere to get into your eye, right? On the other hand, for basic old-style holograms it is actually necessary to use a laser beam to recreate recorded waves. But there is a more "modern" approach called volume holograms, which work in ordinary light.

What i am trying to figure out is how does a hologram work?. More to the point, how is it that rotating a flat holographic sticker allows the virtual object to change orientation - allowing me to see content that was not there a moment ago?

You see objects because your eyes register light that is coming from these objects. If you shift your head, your eyes will be subjected to a different "part" of reflected light waves from those objects, so you will see those objects differently -- for example you will be able to see objects that was obscured before.

Suppose that you have a techique that records completely all the light waves coming from your objects. And you also can "playback" those waves, so that they would exaclty reproduce the lightwaves from real objects. Then no one will be able to distinguish (using only one's eyes) the difference between the real objects and your "lightwave reproduction" of them. If you shift your head, your eyes will be subjected to a different "part" of "reproduced" light waves, so you will see those objects differently -- for example you will be able to "see objects" that was "obscured" before.

That is roughly what holograms do. They record the whole information about the incoming light by storing it in the interference patterns in a film. And when they reflect light they reproduce exactly the lightwaves that was falling on them during recording.

...my credit card:

• has no reference beam
• is not being viewed at a 45 degree angle (meaning no interference can happen)

Well, first about interference -- 45 degree angle is not something that is necessary to see a hologram (though, some holograms can be seen from just a range of some particular angles). More importantly it is not necessary to have interfence or diffraction (diffraction is actually a more appropriate term here).

Now about reference beam. First of all -- you always need "reference beams" to see something. Light have to come from somhere to get into your eye, right? On the other hand, for basic old-style holograms it is actually necessary to use a laser beam to recreate recorded waves. But there is a more "modern" approach called volume holograms, which work in ordinary light.

What i am trying to figure out is how does a hologram work?. More to the point, how is it that rotating a flat holographic sticker allows the virtual object to change orientation - allowing me to see content that was not there a moment ago?

You see objects because your eyes register light that is coming from these objects. If you shift your head, your eyes will be subjected to a different "part" of reflected light waves from those objects, so you will see those objects differently -- for example you will be able to see objects that was obscured before.

Suppose that you have a techique that records completely all the light waves coming from your objects. And you also can "playback" those waves, so that they would exaclty reproduce the lightwaves from real objects. Then no one will be able to distinguish (using only one's eyes) the difference between the real objects and your "lightwave reproduction" of them. If you shift your head, your eyes will be subjected to a different "part" of "reproduced" light waves, so you will "see" those "objects" differently -- for example you will be able to "see objects" that was "obscured" before.

That is roughly what holograms do. They record the whole information about the incoming light by storing it in the interference patterns in a film. And when hologrms reflect (or, sometimes, pass through) light they reproduce exactly the lightwaves that was falling on them during recording.

...my credit card:

• has no reference beam
• is not being viewed at a 45 degree angle (meaning no interference can happen)

Well, first about interference -- 45 degree angle is not something that is necessary to see a hologram (though, some holograms can be seen from just a range of some particular angles). More importantly it is not necessary to have interfence or diffraction (diffraction is actually a more appropriate term here).

Now about reference beam. First of all -- you always need "reference beams" to see something. Light have to come from somhere to get into your eye, right? On the other hand, for basic old-style holograms it is actually necessary to use a laser beam to recreate recorded waves. But there is a more "modern" approach called volume holograms, which work in ordinary light.