The Practical World of Optical Illusions

The Practical World of Optical Illusions

A picture may be worth a thousand words, but the perception of the viewer matters.  Optical illusions focus on the science of optics, which is concerned with both physical and psychological perceptions of light.  Far from being just a game or a party trick, however, optical illusions play an important role in a number of professional fields, including dentistry, entertainment and computer programming and security.

Let’s start with false teeth.  Historically, dentures have been made of a variety of materials, such as bone, metal, porcelain and other people’s teeth.  Today, however, many dental implants, bridges and other devices are made of resin, a sturdy substance which can be colored and molded to fit the needs of the patient.  However, commercially available resins come in only a limited number of colors, not all of which will match a patient’s own tooth color.  In these cases, knowledge of optical illusions, particularly color based optical illusions, can help dentists and patients arrive at a near-perfect color match.

Above: A woman holds a tray with a set of dental resin samples in a variety of shades. Adobe Stock.

Entertainment uses for illusions and manufactured images span centuries, but older optical illusions have come back into vogue.  Pepper’s Ghost, which was invented by John Henry Pepper in 1858 and demonstrated in 1862, has been employed in live shows since the turn of the 21st century as a way to present musical artists who may not be living, or may not even technically exist.  The illusion consists of two panes of glass, one of which is angled at 45 degrees to the other.  An image is reflected off the angled glass and using lighting, curtains and other deflections, the image is projected onto another piece of glass.  Pepper’s Ghost was popular as a theater technique for most of the 1860s and 1870s, but returned as an amusement park trick in the 1960s.  Today, newer patents continue to refine the principles of Pepper’s Ghost, and “holographic” (sic) performances of Michael Jackson lean heavily on modified versions of this very old optical illusion.

1893 Advertisement for “The Original Pepper’s Ghost and the Spectral Opera Company.” National Archives UK, public domain.

Computers and gaming have also adopted elements of optical illusions.  For instance, in 2005, researchers examined the use of optical illusions as a way to ensure people, and not bots, were trying to access a system or social media application.  They explained their findings as a “reverse Turing Test,” using a biological quirk instead of a series of activities as a way to determine whether or not a user was human.  Although this use of optical illusions was not widely adopted, a combination of illusions and gaming has proven successful in a variety of applications.  Elements of gaming and optical illusions have cropped up in unexpected places, such as sea turtle preservation and the restoration of murals.  In these cases, gaming systems and software have been employed to create trompe l’oeil (“trick of the eye”) effects that benefit different fields – in these cases, creating video maps to assist with turtle preservation efforts in Indonesia and reconstructing murals from a church destroyed in 1964.

Optical illusions have lots of useful, practical purposes, but learning about them can be fun for all ages.  Check out the Family R.E.A.D. resource guide for books and activities for youth and families.  Are you or those you know interested in discovering more optical illusions?  Want to find patents based on illusions?  Curious about entertainment, dentistry, gaming or other topics?  Ask Us! or click here:

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