Someone took this rather large round mirror and scanned it with a Canon flatbed. The result was, let’s say, not very mirror-like at all. Actually, the glass area was almost black. So, what’s happened? Where’s the shiny glass mirror we’ve been hoping to see?

To understand why we got the result we did, we need to look at how the scanner works first.

There are many variations in this setup, but at its most basic, here’s what happens after you place a paper document on a glass bed and press “scan”:

• The document is illuminated by a light source through the glass bed. The light source moves along the track as the document is scanned.
• The document is reflected in an angled mirror, which also moves at the same speed along the track.
• The first mirror is captured by a fixed mirror at the other end of the scanner.
• The image from a fixed mirror is captured by a charge-coupled device, or CCD, and can then be saved to a hard drive on your computer.

Here’s what happens when you replace a document with a mirror.

Everything works the same way as before, except that what the movable mirror of the scanner now sees is not a document, but a reflection of what is below. And below is the inside base of the scanner, which is dark. So what your scan will capture is basically a dark reflection, and maybe some fingerprints or light scratches, but no bright objects.

You can have a rear-coated mirror and a front-coated mirror. If you use the first one, the result will be a black copy, and if you use it later, the result will be a blank copy (white). As the rear coated one reflects the scattered light. Mirrors used in photocopier optics to achieve optical distance are front coated.

Another Explanation

The full output will be black, because the photocopy machine generates the result after reflecting the light to the white portion of the original copy, sir, in your case, if the mirror is placed, the whole light will reflect the result as a completely black print.

The Process of Photocopying

The original document is illuminated by a bright lamp, and the white areas of the original document reflect the light on the surface of the photoconductive drum. The areas of the drum which are exposed to light become conductive and therefore discharge to the ground. The area of the drum not exposed to light (the areas corresponding to the black portions of the original document) remains negatively charged. The result is a latent electrical image on the drum surface.

The ideal mirror has perfect reflectivity, no specularity, no opaqueness. Moost copying machines are designed for materials that can be more or less opaque, high specularity and relatively low reflectivity. I can see at least 3 possible results for the mirror experiment, depending on the design of the copying machine. As mentioned above, the light source and the detector are usually out of line giving you black as a result. If the detector and the light source are inline, the image will be saturated white. If the detector is a ccd camera, the image would be a bit out of the camera focus (assuming diffuse illumination).