Optical Illusion An optical illusion (also called a visual illusion) is characterized by visualll perceived images that differ from objective reality. The information gathered by the eye is processed in the brain to give a percept that does not tally with a physical measurement of the stimulus source.

three main types Optical Illusion 1. literal optical illusions that create images that are different from the objects that make them, 2. physiological ones that are the effects on the eyes and brain of excessive stimulation of a specific type (brightness, tilt, color, movement), and 3. cognitive illusions where the eye and brain make unconscious inferences. They can also be known as "mind games".

Hermann grid illusion characterised by "ghostlike" grey blobs perceived at the intersections of a white (or light-colored) grid on a black background. The grey blobs disappear when looking directly at an intersection. An example of the Hermann grid illusion. Dark blobs appear at the intersections

Grid Illusion A grid illusion is any kind of grid that deceives a person's vision. The two most common types of grid illusions are Hermann grid illusion and the Scintillating grid illusion.

A scintillating grid illusion discovered by E. Lingelbach in 1994 A scintillating grid illusion. Shape, position, colour, and 3D contrast converge to produce the illusion of black dots at the intersections.

Same color illusion also known as Adelson's checker shadow illusion, checker shadow illusion and checker shadow—is an optical illusion published by Edward H. Adelson, Professor of Vision Science at MIT in 1995. The squares A and B on the illusion are the same color (or shade), although they seem to be different. This can be proven by sampling the colors of A and B in an image-editing program. By erasing everything except the two labeled squares, the illusion is dispelled.

Same color illusion

Afterimage an optical illusion that refers to an image continuing to appear in one's vision after the exposure to the original image has ceased. One of the most common afterimages is the bright glow that seems to float before one's eyes after looking into a light source for a few seconds. The phenomenon of afterimages may be closely related to persistence of vision, which allows a rapid series of pictures to portray motion, which is the basis of animation and cinema.

Motion aftereffect http://upload. wikimedia

Cognitive illusions Cognitive illusions are assumed to arise by interaction with assumptions about the world, leading to "unconscious inferences", an idea first suggested in the 19th century by Hermann Helmholtz. Cognitive illusions are commonly divided into ambiguous illusions, distorting illusions, paradox illusions, or fiction illusions.

Ambiguous illusions are pictures or objects that elicit a perceptual 'switch' between the alternative interpretations. The Necker cube is a well known example; another instance is the Rubin vase.

Construction The distinction is exploited by devising an ambiguous picture, whose contours match seamlessly the contours of another picture (sometimes the same picture; a practice M. C. Escher used on occasion) or more often another picture. The picture should be "flat" and have little (if any) texture to it. The stereotypical example has a vase in the center, and a face matching its contour (since it is symmetrical, there is a matching face on the other side).

Ambiguous illusions Rubin’s Vase/Face The Division Bell by Pink Floyd

Transformation

Distorting illusions are characterized by distortions of size, length, or curvature. A striking example is the Café wall illusion. Another example is the famous Müller-Lyer illusion.

Paradox illusions http://www.scientificpsychic.com/graphics/ are generated by objects that are paradoxical or impossible, such as the Penrose triangle or impossible staircases seen, for example, in M. C. Escher's Ascending and Descending and Waterfall. Paradoxes--in which the same information may lead to two contradictory conclusions--give us pleasure and torment at the same time. They are a source of endless fascination and frustration, whether they involve philosophy (consider Russell's paradox, "This statement is false"), science--or perception. http://www.sciamdigital.com/index.cfm?fa=Products.ViewIssuePreview&ARTICLEID_CHAR=9F16C230-2B35-221B-6E6B49A6CC2EA61E

Maurits Cornelis Escher (17 June 1898 – 27 March 1972) a Dutch graphic artist. He is known for his often mathematically inspired woodcuts, lithographs, and mezzotints. These feature impossible constructions, explorations of infinity, architecture, and tessellations.

Penrose triangle The triangle is an illusion dependent on a cognitive misunderstanding that adjacent edges must join.

The Penrose triangle also known as the Penrose tribar, is an impossible object. It was first created by the Swedish artist Oscar Reutersvärd in 1934. The mathematician Roger Penrose independently devised and popularized it in the 1950s, describing it as "impossibility in its purest form". It is featured prominently in the works of artist M. C. Escher, whose earlier depictions of impossible objects partly inspired it.

The three hares is a circular motif which appears in sacred sites from the Middle and Far East to the churches of south west England (where it is often referred to as the "Tinners’ Rabbits").

Fictional illusions defined as the perception of objects that are genuinely not there to all but a single observer, such as those induced by schizo’phrenia or a ha’llucinogen. These are more properly called hallucinations.

Multi-Stability vs. Uncertainty Principle 267-272 In quantum mechanics, the Heisenberg uncertainty principle states by precise inequalities that certain pairs of physical properties, such as position and momentum, cannot be simultaneously known to arbitrarily high precision. That is, the more precisely one property is measured, the less precisely the other can be measured.

Visual Clues & Perspective Most optical Illusions depend on the techniques and conventions of drawing. The illusion is that you are seeing a 3 dimensional object, but you are looking at a 2 dimensional construction. ALWAYS ASK: HOW WAS THIS PICTURE MADE?

How many legs?

Monkey King’s Eyes Penetrating Insight 火眼金睛 【huǒyǎnjīnjīng】 piercing eye; penetrating insight main character in the classical Chinese epic novel Journey to the West (西遊記).