Introduction: Pinhole Eye Model

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Ahoy there, matey! Prepare to get kicked in the eyeballs with this wonder of a vision modification!

The pinhole eye model is a great way to see how squids and octopus see the world, and you'll get a bit of a surprise looking through it. I often preface making this with my students as it revealing "the great lie your eyes tell you." Let's see how!

  • What: Pinhole Eye Model
  • What!?: Oh, just make it
  • Concepts: vision, lenses, focus
  • Materials:
    • Wax Paper
    • Rubber band(s)
    • Two different diameter cardboard tubes (one should be able to fit inside the other)
    • Magnifying lens
    • End for one tube (can make out of cardboard if needed)
  • Tools:
    • X-acto blade
    • Hot glue gun / hot glue

Eye'm excited!

Step 1: Prep Inner Tube

Cut a length of the smaller diameter tube that's a little longer than your wider one. Pull wax paper across one end so it is fairly tight, and secure it with rubber bands. Feel free to cut off extra bits with scissors.

If you can't find tubes, you can do this with just about anything! Two cups with the bottoms cut out work well, too.

Step 2: Make Lens Holder

Okay, so it's not quite a pinhole, but it's the same concept. If you have the end of a mailer tube, that makes things super easy. Pop out a magnifying lens from somewhere, cut a hole large enough, and hot glue it in the end of the cap. If you don't have a cap, make one out of cardboard and glue it on!

It's great to experiment with different lenses with different focal lengths, so making multiple that you can switch out is pretty fly.

Step 3: Scope Your World

Telescope your two tubes, until you see the world projected on your wax paper! It will come in to focus at just one spot perfectly, and that's the focal length of your lens.

Grab different lenses to find other focal lengths and behaviors as well! If you really want to up it up, you can make a large one out of a box that can take camera lenses.

Some science notes:

  • You'll find that your whole world is flipped upside-down, which is how your retina experience it, too! There's a great article here about the process of flipping vision in your brain.
  • Focal lengths are at play here, and are a great subject in optics. Check out the wiki here.
  • This model eye is close to the way octopus and squids see as they adjust the distance and angle of a hard lens at the front of their eye to project differently on to their optic nerve (in our model, the wax paper) to focus on different things. For humans and many terrestrial animals, we have a soft lens that we adjust the shape of with muscles.

Eye hope you enjoy!