Thanks to Clay Daetwyler and Richard Berg

Talk dedicated to the memory of Dan Margulies

of

The University of Maryland Lecture-Demo Program

http://www.physics.umd.edu/lecdem/

Seeing the Light

The Art and Science of Optical (Visual) Illusions

Rajarshi Roy

Institute for Physical Science and Technology Department of Physics

Institute for Research in Electronics and Applied Physics University of Maryland, College Park

MD 20742 USA rroy@umd.edu

Seeing is believing!

Life begins

Our eyes

Optical illusions: simple apparatus, complex results!

Now you see it, now you don’t -

Perspectives in light, reference frames

Light and dark, feedback loops, brain and body

Wake up, look and listen!

Hermann von Helmholtz

(1821 –1894)

Foundations of

vision and hearing

EYE

Opthalmoscope

Normal Retina

Retinitis Pigmentosa

A form of retinal dystrophy, RP is

caused by abnormalities of the photoreceptors (rods and cones) or the retinal pigment epithelium (RPE) of the retina leading to progressive sight loss.

http://en.wikipedia.org/wiki/Retinitis_pigmentosa

Glaucoma

Glaucoma is an eye disease in which fluid pressure within your eye becomes

too high, damaging the delicate fibres of the optic nerve which carries visual

impulses from your eye to the brain. This damage is irreversible and can lead to

blindness in advanced cases. Glaucoma accounts for 40 per cent of blindness in

Singapore.

http://www.snec.com.sg/eye-conditions-and-treatments

Eye Accommodation

Accommodation change with age (from R. Gregory, Eye and Brain)

Eye problems

First eyeglasses – Venice 1286?

Adrishya Alok

1888-1894: As German physicist Heinrich Hertz proves experimentally the existence of electromagnetic waves in free space, Bose starts pursuing follow-up microwave research, and ultimately succeeds in reducing the wave-length to the millimetre level.

1895: In a public demonstration at the Town Hall in

Kolkata, in presence of Sir William Mackenzie, the Lieutenant Governor of Bengal, Bose ignites gunpowder and rings a bell at a distance using millimetre range wave-length microwaves. Writes an important essay, titled

Adrishya Alok (Invisible Light), in Bengali.

J. C. Bose (1858 – 1937)

Teachers at Cambridge: Lord Rayleigh (Physics), Sir Francis Darwin (Botany)

Millimeter wave research

Proc IEEE 86, 259-285 (1998)

P. K Bondyopadhyay

Sir J.C. Bose’s diode detector….

An early U S Patent from India

Detecting electromagnetic radiation

http://history-computer.com/ModernComputer/Basis/transistor.html

The first person who applied semiconductors for practical purposes, was the Indian polymath Sir Jagadish Chandra Bose (1858-1937). Jagadish Chandra Bose was a physicist, biologist, botanist, archaeologist, and writer of science fiction. To detect radiation, he used a variety of different metal semiconductor junctions connected to a highly sensitive galvanometer in series. He invented several semiconductor devices, the first of which was his Galena detector, which he invented some time during 1894-1898, and demonstrated in Royal Institution Discourse in 1900. In this device, a pair of point contacts (cat whiskers), in this case of galena, was connected in series with a voltage source and a galvanometer. This device could detect any kind of radiation, Hertzian waves, light waves, and other radiation.

He called his galena point contact detector an artificial retina (because by suitable arrangement it could be made to detect only light waves), a universal radiometer. Bose was awarded the first patent for a semiconductor device in the world, namely for the Galena detector. Among his other pioneering solid-state semiconductor receivers are the spiral spring coherer and iron-mercury- iron coherer (detector) with a telephone.

Artificial retina today

Attorney Dean Lloyd sits at his office in Palo Alto, California.

Lloyd, who went blind from retinitis pigmentosa, had experimental

electrodes implanted in the back of his right eye. Lloyd wears

black sunglasses containing a tiny camera and transmitter, a video

processor and battery pack on his belt. Lloyd is among only 10

people in the United States to undergo the procedure.

/www.vcstar.com/photos/2010/feb/24/88452/#ixzz1GDwjSvyv

-

Signals from the brain: Hans Berger

Hans Berger and the EEG

David Millett, Perspectives in Biology and Medicine, volume 44, number 4 (autumn 2001):522–42

© 2001 by The Johns Hopkins University Press

The Brain(s) at work Basic Features of the Cortex

Hongdian Yang Woodrow Shew

Shan Yu Dietmar Plenz

The cortex

• Excitatory & inhibitory neurons

• Excitation and inhibition must be balanced

Too much excitation: epilepsy

Too little excitation: insensitive to inputs

Proper function: avoid extremes

• Outmost layer

• IMPORTANCE

http://www.dartmouth.edu/~rhg/brainareas.html

Neurons are spontaneously active

Neuronal avalanches, scaling and response to external stimuli

H S M (“Donald”) Coxeter

Geometer

(1907 – 2003)

“Discovered” and inspired Escher

Great website for illusions

• http://www.michaelbach.de/index.html

Recognizing faces

Recognizing Faces

Unrelated look-alikes ??

• http://www.google.com/search?q=francois+

brunelle&hl=en&safe=off&biw=1106&bih

=580&prmd=ivnso&tbm=isch&tbo=u&sour

ce=univ&sa=X&ei=71gkTqzfAoj40gGrusn

ZAw&sqi=2&ved=0CDEQsAQ

• Francois Brunelle, Montreal

A “New” Illusion

Thompson effect - 1

Thompson effect - 2

Thompson, P. (1980)

Margaret Thatcher:

a new illusion. Perception 9:483–484

Head spin trick

http://www.artsology.com/giuseppe.php

Giuseppe Arcimboldo (1527-1593) (Thanks, Brian H! )

Can the eye see a single photon?

ENERGY, QUANTA, AND VISION

SELIG HECHT, SIMON SHLAER, AND MAURICE HENRI PIRENNE

(From the Laboratory of Biophysics, Columbia University, New York)

(Received for publication, March 30, 1942)

The Journal of General Physiology

“the range of 54 to 148 quanta at the cornea becomes as an upper limit 5

to 14 quanta actually absorbed by the retinal rods. This small number of

quanta, in comparison with the large number of rods (500) involved,

precludes any significant two quantum absorptions per rod, and means

that in order to produce a visual effect, one quantum must be absorbed by

each of 5 to 14 rods in the retina.”

Response in the Living and Non-Living

Jagadis C. Bose

LONGMANS, GREEN, AND CO.

39 PATERNOSTER ROW, LONDON

NEW YORK AND BOMBAY

1902

Bose and his students, 1928

Sitting from left to right: Meghnad Saha, Jagadis Chandra Bose,

J. C. Ghosh

Standing from left to right: S. Datta, S. N. Bose, D. M. Bose, N. R. Sen

J. N. Mukherjee, N. C. Nag

“The case of the wandering light” The Autokinetic Illusion gives you the impression that a stationary object is moving in

front of the airplane's path; it is caused by staring at a fixed single point of light (ground

light or a star) in a totally dark and featureless background. This illusion can cause a

misperception that such a light is on a collision course with your aircraft

FAA, Office of Aerospace Medicine (OAM)

Washington, D.C

Parkinson’s disease • Parkinson's is caused by a shortage of a chemical

messenger, dopamine, in the brain. Dopamine is

a key neurotransmitter involved in motor control.

• Scientists suspect that PD is caused by a complex

interaction between genes and the environment.

Environmental toxins play a role in triggering the

disease, although no one knows which toxins, or

why they trigger the disease in some people and

not others.

Feedback control of movements

Multiple Sclerosis (MS)

What happens in MS • During periods of multiple sclerosis activity, white blood

cells (leukocytes) initiate and take part in what is known as the inflammatory response. During the inflammation, the myelin gets stripped from the axons in a process known as demylination.

• The effect of this has many parallels to the rubber insulation on wire perishing - some or all of the electricity in the wire could short out and the efficient conductivity of the wire could be reduced. When the myelin sheath is damaged, the transmission of nerve impulses is slowed, stopped or can jump across into

other demyelinated axons.

(NIH description)

Optical illusions –

what are they good for?

A vision problem is the first symptom of Multiple Sclerosis (MS) for many people. The sudden onset of double vision, poor contrast, eye pain, or heavy blurring is frankly terrifying—and the knowledge that vision may be compromised makes people with MS anxious about the future.

Fortunately, the prognosis for recovery from many vision problems associated with MS is good.

A vision problem is the first symptom of Multiple Sclerosis for many people. The sudden

onset of double vision, poor contrast, eye pain, or heavy blurring is frankly terrifying—and the knowledge that vision may be compromised makes people with MS anxious about the future. Fortunately, the prognosis for recovery from many vision problems associated with MS is good.

Brain (1975) 98, 283-296

USE OF THE PULFRICH PENDULUM

FOR DETECTING ABNORMAL DELAY

IN THE VISUAL PATHWAY IN

MULTIPLE SCLEROSIS

DAVID RUSHTON

{From the Medical Research Council Neurological Prostheses Unit, and the

Department of Neurology, Institute of Psychiatry, De Crespigny Park, London SE5

8AF)

Pulfrich Pendulum

“VON C. Pulfrich (1922) described an illusion in which a pendulum swinging at

right angles to the line of gaze appears to swing in an elliptical path when a

dark glass is placed in front of one eye.

He suggested that the illusion was caused by a prolongation of the latency of vision

of the dimmed eye, causing a disparity between the perceived image of the moving

bob from the two eyes and hence an illusion of displacement in depth. Pulfrich

illustrated his explanation of the phenomenon with the words of Gurnemanz in

"Parsifal"; "Du siehst, mein Sohn, zum Raum wird hier die Zeit.―

The binocular disparity is proportional to the velocity of the bob, so that for a

pendulum in simple harmonic motion the perceived motion is elliptical. The

direction is clockwise, viewed from above, if the left eye is dimmed, and

anticlockwise if the right eye is dimmed. If Pulfrich's explanation of his

phenomenon is correct, and Julesz and White (1969) have given good evidence that

it is, then the delay in the dimmed eye can be calculated from the dimensions of the

ellipse.‖ (Rushton)

Visual latency

• Bio-feedback loop

• Measure latency time with a meter stick!

SQRT(2D/g)

(g ~ 10 m/s/s)

A LIGHT THOUGHT FOR THE ROAD

Application of the Scientific Method

A biological researcher experimented with a flea, which has six legs.

He puts it on the table and says: "Jump!" The flea jumps 3 meters, so he writes down to his log:

"The flea has jumped 3 meters." Afterward he cuts one of its legs off and says again: "Jump!" The flea jumps only 2 meters, so he writes down to the log:

"The flea has jumped 2 meters." Then he again cuts one more leg, again says: "Jump!" It jumped 1.5 meters, which was also registered in the log.

He continued cutting the fleas' legs until there were no legs left, he puts it on the table and says: "Jump!" The flea doesn't move. He says again: "Jump!" It doesn't move. So he writes down

"After removing all legs of the flea, the flea loses its ability to hear.“

A very nice reproducible experiment !

Father William

“You are old, Father William,” the young man said, “And your hair has become very white; And yet you incessantly stand on your head – Do you think, at your age, it is right?” “In my youth,” Father William replied to his son, “I feared it might injure the brain; But, now that I'm perfectly sure I have none, Why, I do it again and again.”

Lewis Carroll, Alice's Adventures in Wonderland (1865)