Question About Hologram Property - Seeking Answers

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Discussion Overview

The discussion revolves around the properties of holograms, specifically how they can project patterns of light when illuminated by a laser. Participants explore the mechanics of holography and the nature of the images or patterns produced, comparing them to traditional lenses and addressing misconceptions about holographic projections.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the validity of seeing an image on a wall through a hologram, suggesting that a lens is typically required for image resolution.
  • Another participant asserts that a hologram can function like a lens, capable of producing various patterns of outgoing light rays when illuminated by a laser.
  • A participant expresses confusion about the nature of the projection, comparing it to a scenario where a star-shaped object emits light, questioning if it would appear blurry on a wall.
  • One response clarifies that the hologram splits the incoming laser beam and directs copies of the beam at different angles, resulting in a pattern rather than a true image.
  • A participant inquires if the pattern seen on the wall resembles the three-dimensional appearance of the hologram itself.
  • Another participant clarifies that the pattern is a two-dimensional arrangement of points and that viewing the hologram does not yield the same effect as a transmission hologram.

Areas of Agreement / Disagreement

Participants express differing views on the nature of the projections from holograms, with some asserting that they can create patterns similar to images while others emphasize the distinction between patterns and true images. The discussion remains unresolved regarding the exact nature of holographic projections.

Contextual Notes

There are assumptions about the definitions of images and patterns in holography that are not fully explored. The discussion also reflects varying interpretations of how holograms function in terms of light manipulation.

Ja4Coltrane
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Someone I know has asked about a certain property of holograms which he said he was shown while he was in school, but i can't figure out why the property should be true.

He says that he once saw a video of a demonstration where a light (presumably a laser) was shone through a hologram, and the image could be seen on the wall behind the hologram.

This doesn't seem to make sense to me. I thought that a lens would be needed to resolve the image onto a screen.

Any help is appreciated!
 
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A hologram can act like a lens.
The pattern on the wall isn't strictly speaking an image, you can produce a hologram which will create pretty much any pattern of outgoing light rays when you shine a laser through it.
That's how the add-on lenses for laser pointers that project a line or star or other shapes work - they are holograms.
 
mgb_phys said:
A hologram can act like a lens.
The pattern on the wall isn't strictly speaking an image, you can produce a hologram which will create pretty much any pattern of outgoing light rays when you shine a laser through it.
That's how the add-on lenses for laser pointers that project a line or star or other shapes work - they are holograms.

I'm still confused. Is this just like if I have say, a stars shaped object that happens to send light out from every point, then if I look at a wall next to it, I will see a blurry star?
 
No, the hologram splits the incoming laser beam and sends out copies of the beam at different angles.
If you get the arragement of the angles right they make a pattern on the wall.
It's not an image because it makes the same pattern although at a different scale at different distances.

If you prefer you can think of the hologram as being a grid of little mirrors (or prisms) each bending the incoming light in a particular direction
 
Okay and the pattern you see on the wall looks like the three dimensional thing that you see when you look into the hologram?
 
No it's just a 2d pattern of points.
You generally can't see anything looking into this kind of hologram - it's not the same effect as projecting a transmission hologram.
 

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