3-Dimensional Airy Disk Animation
Jan 8th, 2008 by Leo Geis
This is a 3-Dimensional Adobe Flash rendering of Circular Aperture Diffraction (an Airy Disk) forming. It is not to scale…and slowed a wee bit.
The animation occurs in the following sequence:
- The aperture rotates so that you can acquaint yourself with its simplicity.
- A light ray approaches stealthily and at high speed, probably from a beautiful wintery mountain scene.
- Upon passing through the aperture, the light beam begins to disperse, or Diffract. Light is incorrigible that way.
- The Airy Disk is kind enough to pause until you click the button to replay. We have very polite light in Idaho.
Please remember that we are not dealing with Refraction, which is an entirely different issue. In fact, that’s why I avoided using Red, Green, and Blue as the colors for my Diffraction Rings. I suppose that technically the outer Diffraction Rings in the animation should be biased Red (longer wavelengths Diffract more aggressively), but I had already selected a very cool background that wouldn’t contrast well with Red.
The actual number of Diffraction Rings, their intensity and specific behavior will vary with each circumstance-including the size of the aperture. Here’s an excellent 2D demonstration that also touches upon (although it doesn’t say so…) the Rayleigh Criterion.
The size of the Airy Disk, the terminus of the ray, is a major concern in optical systems and the source of a great deal of debate on the limits of classic photographic spatial resolution. As you research the matter, just keep in mind that Diffraction is not the only derogatory effect a camera/optical system introduces into an image. You’ll need to take into account all of those other bizarre things we’ve covered previously to really understand the matter.
Incidentally, if you’re interested in the metrics, visit here.
…and if that’s just not enough good information, try this.
Here’s a more sophisticated 3D (but with a very low frame rate and quality of render) animation of Airy Disks encountering a Bayer Array:
- Medium Quality (2MEG)
- High Quality (7.68MEG)
L