I’ve been messing about with laser beams this week and put together a demonstrative worth sharing.

As any teacher will tell you, it takes a lot of effort to understand something well enough to teach it. I’m always looking for ways to better understand concepts I teach, and just as importantly, to figure out how to relay that information to students more clearly.

So I was pumped when I came across this Laser Ray Box from Arbor Scientific. It offers a hands-on way to explore how light makes its way to a camera sensor, which is a key component of photogrammetry and video analysis.

Check out the video below, for example:

It demonstrates several key ideas:

  1. Light generally passes straight through a rectangular prism.

  2. Light diverges after interacting with a concave lens.

  3. Light is focused by a convex lens.

  4. The distance from the convex lens to the intersection of the beams is constant and called the focal length.

  5. When those intersecting beams align with the sensor (gray rectangle in the video), the image is in focus. That’s what you’re doing as you focus your camera, moving the lens with respect to the sensor.

  6. Light traveling through a curved lens is distorted unless it passes through the optical axis (center). The farther from the optical axis, the greater the distortion. Note: correcting this distortion is often part of a high-accuracy project.

  7. A convex lens combined with a concave lens creates the ability to change the focal length. That’s how zoom cameras work, by moving lens elements relative to each other.

That little experiment blew my hair back and had my brain racing for a couple of days. I don’t think I’m done digesting the information or making all the connections yet, but I’m further along than I was last week.

Hopefully this betters your understanding of light too. It’s a wild topic. If you really want to break your brain before the weekend, check out the double-slit experiment.

Thanks to Alan Walford of PhotoModeler for QCing this email and thanks to you for reading... keep learning!

Lou Peck
​Lightpoint | JS Forensics​

P.S. Speaking of crazy light.

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