Pinhole Projector: How Many Photons, How Small a Hole for Shape?

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SUMMARY

The discussion centers on the mechanics of a pinhole projector, specifically regarding the number of photons required and the size of the pinhole necessary to maintain the apparent shape in the projection. It is established that a single photon is insufficient to convey shape, while a pinhole that is too small can lead to diffraction and interference. However, typical pinholes used in pinhole cameras are sufficiently large to avoid these issues, allowing for effective image formation during events like eclipses. The preservation of directional information from incoming photons is crucial for forming a coherent image.

PREREQUISITES
  • Understanding of basic optics principles
  • Knowledge of photon behavior and light propagation
  • Familiarity with diffraction and interference phenomena
  • Concept of image formation in pinhole cameras
NEXT STEPS
  • Research the principles of diffraction and how it affects image quality in optical systems
  • Explore the design and functionality of pinhole cameras
  • Study the relationship between photon count and image clarity in optical projections
  • Investigate the effects of varying pinhole sizes on image resolution and sharpness
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Physics students, optical engineers, photography enthusiasts, and anyone interested in the principles of light and image formation using pinhole projectors.

mishima
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I'm confusing myself trying to explain the pinhole projector (card with pin point hole used to watch eclipses). How many photons are required, or how small a hole could you maintain, to still get the apparent shape in the projection? Why? Obviously only one photon isn't enough to describe the shape in a projection, and too small a hole would eventually produce diffraction and interference. Any thoughts?
 
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You are correct. But a pinhole is not small enough to introduce those effects. Or at least not on a scale big enough to cause an issue with general observing on an eclipse.
 
mishima said:
I'm confusing myself trying to explain the pinhole projector (card with pin point hole used to watch eclipses). How many photons are required, or how small a hole could you maintain, to still get the apparent shape in the projection? Why? Obviously only one photon isn't enough to describe the shape in a projection, and too small a hole would eventually produce diffraction and interference. Any thoughts?

Consider the fact that the object is of finite size- if you like, photons are entering the pinhole from different directions. As long as that directional information is preserved, you will form an image. Pinholes in cards are many wavelengths in diameter- so you can see just fine with a 'pinhole camera'.
 

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