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What Would Happen If You Put A Mirror In A Scanner?

By Quora on at

By Archie D'Cruz

Let's find out, shall we?

I took a fairly large round mirror and scanned it using my Canon flatbed. The result was… let's say, not very mirror-like at all. In fact, the glass area was almost black.

What Would Happen If You Put A Mirror In A Scanner?

So what happened? Where's the shiny glass mirror we were hoping to see? To understand why we got the result we did, we first need to look at how a scanner works.

There are many variations of this setup, but at its most basic, here's what happens after you place a paper document on the glass bed and press "Scan":

What Would Happen If You Put A Mirror In A Scanner?

  1. A light source illuminates the document through the glass bed. The light source moves along a track as the document is being scanned.
  2. The document is reflected into an angled mirror, which also moves along a track at the same speed.
  3. The first mirror's reflection is captured by a fixed mirror at the other end of the scanner.
  4. The image from the fixed mirror is captured by a CCD (charge-coupled device) and can then be saved to a computer hard-drive.

This is another way of looking at it, with a three-mirror setup.

What Would Happen If You Put A Mirror In A Scanner?

Now here's what happens when you replace the document with a mirror:

What Would Happen If You Put A Mirror In A Scanner?

Everything works the same way as before, except that what the scanner's movable mirror sees now is not a document, but a reflection of what is below. And what's below is the inside base of the scanner, which is black.

So what your scan will capture is essentially a dark reflection, and maybe some fingerprints or light scratches… but no shiny objects.

Images: Wikimedia Commons, Quora


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