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Pre-Nineteenth Century History of Optics Motivating Eye Care Technology |
Karan R. Gregg
Aggarwala, OD (NIH Equiv.), MS, PhD, FAAO
Founder-President, Ben
Vision Research, Inc., July, 2013 CE, New York, NY
Introduction
In chronological order by year of
birth, this list of famous people (born 1801 or before) and their brief
biographies, documents the major achievements of pre-modern
philosophers, mathematicians, physicists, scientists and optical
engineers-- because of whose pioneering discoveries and inventions,
current-day optical, optometric, and ophthalmic instrument development
became permissible and was realized. These biographies include people
born in, or working-- in Europe, the United States of America, and the
Near East. Biographies from other world regions are not in this review.
Criteria for Inclusion
The famous people selected in
this list of biographies have been selected based on various criteria—
some based on my memory of their known contributions, and others based
on subject area searches. These criteria may not be comprehensive. The
one easily definable item these outstanding personalities share in
common is their inclusion in the Hutchinson Dictionary of Scientists1.
This inclusion criterion is good but has its problems. For example,
Lambert is more famous than Lippershey or Ritter, yet Lambert’s
biography was missing in the Hutchinson Dictionary of Scientists and was
not present in The Physics Book2.
I did not want to use any
internet resource other than www.en.wikipedia.org and when I did not
find Lambert there, I decided not to include him. It is likely that
there would be many other scientists who may have been omitted in this
article. For this, an apology is offered along with the excuse of
sourcing consistency.
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Pythagoras c. 580- 500 BC:
An early philosopher and mathematician of ancient Greece, Pythagoras
classified numbers and gave them mystical properties.
Born on the island
of Samos, he fled a despotic ruler to found a school and brotherhood in
Croton, South Italy. The school lasted a little over 50 years until it
was suppressed for political and religious reasons.
The
Pythagoras theorem equates the square of the length of the hypotenuse of
a right-angled triangle to the sum of the squares of the lengths of its
perpendicular sides.
Pythagoreans formulated the theory of proportions
(ratios and fractions), which helped them understand and describe the
harmonic motion of musical strings. Harmonic analysis forms the
fundamentals of Fourier-optics, and finds its roots in the work of
Pythagoras. |
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Euclid c. 330 – c. 260 BC: This famous
mathematician used logical steps to deduce known principles of
mathematics and geometry from the unknown, by what is known as
the synthetic method.
Using analytical techniques, he
developed axioms of Euclidean geometry from conjectures and
hypotheses.
Euclid set up a school of mathematics in
Alexandria (now in Egypt). His works were translated first into
Arabic by Alhazen, and then into Latin, and from both of these
languages, into various European languages.
Geometry
applies directly to optics because light tends to travel in
straight lines except under the influence of strong
gravitational fields (Einstein’s General Theory of Relativity),
or from aperture edge-effects (diffraction), or optical
media-interface effects (refraction, reflection). |
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Ptolemy 100 to 170 CE: Born on the banks of the Nile in the town of Ptolemais Hermii, Ptolemy worked in Alexandria in an observatory set up
at the top of a temple. Said to be inspired by Plato, Ptolemy worked on
the assumption that the earth was shaped like a perfect sphere. The
calculation of projections onto a spherical surface has applications in
visual field testing (perimetry) and retinal mapping. Ptolemy’s
Geography was a standard source of information until the 16th Century—
based on his maps of Asia and large parts of Africa. His system of an
earth-centred universe was toppled in 1543 by the astronomer Copernicus.
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Ibn al-Haytham Alhazen 965-1038 CE: Alhazen’s
book of optics, Kitab al-Manazir, was translated from Arabic to
Latin as Opticae thesaurus (1572). His original comprehensive
contributions were based on his experiments and on his study of
Greek literature, and were considered authoritative.
Alhazen challenged the view held by Hero and Ptolemy that rays
first emerge from the eye, capture the form of the object, and
return to the eye as an eidola. Instead he proposed that light
emerging from the sun is reflected by objects and enters the eye
to produce the sensation of vision.
Alhazen studied the
image-forming properties of spherical and parabolic mirrors, and
measured the refraction of light by lenses.
His Book of
Optics was utilized by near-Eastern philosopher-scientists (e.g.
al-Farisi 1267-1320), and Western scientist-monks (e.g.
Theodoric 1250-1310), well into the period of the Renaissance. |
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Leonardo da Vinci
1452-1519 CE: Da Vinci received formal elementary education,
and was apprenticed at the age of about 14 by his father, to the artist
Andrea del Verrocchio4 in whose guidance he learned about artistic,
technical and mechanical subjects. Between 1490 and 1495 he produced his
well-known notebooks in mirror-writing. Leonardo explored the science of
painting and documented the visual cues that lead to monocular depth
perception, such as geometric perspective, atmospheric haze, distance
and direction of sources of illumination, and length, depth and
direction of shadows.
Da Vinci also developed a theory of
mechanics based on friction and resistance, with illustrations of gears,
screw-based cutting machines, and hydraulic jacks. The total number of
inventions attributed to Leonardo is a staggering three hundred!
Leonardo studied the flight of birds, forming the basis for modern
avionics. After 1503, he conducted hydrological studies for civil
engineering projects and for the circulatory system of the heart, which
today form the roots for the study of blood flow dynamics. Da Vinci was
born in Tuscany, lived in Florence and Milan, and spent his last years
in Rome and Amboise (France). |
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| Hans Lippershey
1570-1619 CE: This German-born Dutch spectacle lens-maker is
often credited with inventing the refracting telescope in 1608.
Lippershey's original instrument (with 3 times magnification) was termed
“Dutch perspective glass,” and consisted of either two convex lenses
producing an inverted image, or a convex objective and concave eyepiece
leading to an upright image. The term "telescope" was coined three years
later by Giovanni Demisiani. The ophthalmic lens industry started in
Venice and Florence in the thirteenth century, and later expanded to the
Netherlands and Germany. |
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| Christoph Scheiner
1573-1650 CE: In about 1605, Scheiner invented the pantograph,
an instrument for making scaled copies of schematics. Scheiner built his
first telescope in 1611 and projected the image of the sun onto a white
screen. His observations of “sunspots” and the attribution to
“refraction” of the apparent elliptical form of the sun near the horizon
are commendable. Scheiner also proposed that Venus and Mercury revolved
around the sun and due to his fear of religious or political adversity
his data were communicated under a pseudonym to Galileo and Johannes
Kepler. Ophthalmic optical instrument designers are well aware of the “Scheiner
disc” which contains a double pin-hole that determines focus of optical
systems and can help distinguish between myopic and hyperopic focal
planes of the eye. |
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Willebrord van Roijn Snell 1581-1626 CE: Born
in Leiden, Snell developed the method of triangulation in 1615,
from which he made an accurate determination of the radius of
the Earth.
Calculations of the sagittal depth of
spherical lenses are based on the same triangulation formulae.
Snell devised the basic law of refraction- which states that the
ratio of the sine of the angle of incidence to the sine of the
angle of refraction is a constant.
When the first medium
is a vacuum or air, the Snell ratio equals the refractive index
of the refracting (second) medium.
Snell’s law was published by
the mathematician Descartes in 1637, and forms the basis for all
monochromatic refraction by lenses and prisms. |
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| Isaac Newton
1642-1727 CE: Newton was born in Lincolnshire and studied at
Cambridge where he became a professor at age 26. His theories were
consistent with the laws of planetary motion developed by Johannes
Kepler, and Kepler’s laws helped Newton define the terms mass, weight,
force, inertia, and acceleration. Newton and Leibniz worked
independently on the development of differential calculus. Newton’s
experiments on dispersion of white light through prisms of glass
inspired him to minimize chromatic aberration by using mirrors instead
of lenses in his telescope. His experiments on light and colour were
conducted in a darkened room with a slit-beam of sunlight entering
through a window. Besides geometric optics, Newton investigated
thin-film interference and gravitation. Robert Hooke claimed to have
discovered the inverse-square law of gravitation prior to Isaac Newton. |
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Benjamin Franklin 1706-1790 CE: The inventor of
bifocal spectacles, Benjamin Franklin has been an inspiration to
almost all Americans who believe in the values and principles of
the founding fathers of the constitution. Aside from his
late-life service as ambassador to France and his prior founding
of the Post Office, Ben Franklin is famous for his 1752 “kite
and key experiment” (considered dangerous to repeat) conducted
just prior to a thunderstorm—which proved that lightning is a
form of electricity that can be harnessed and stored in a Leiden
jar (capacitor). Franklin distinguished between positive and
negative electricity, and his observations predate the more
quantitative research of Volta (1745-1827) that formed the basis
for the flow of electrical current. |
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It is less commonly known that Benjamin Franklin conducted
experiments on thermometer readings underneath
sunlight-illuminated cloths of various colours.
These
experiments suggested that absorbed visible radiation (light) of
varied spectral composition may be specified as elevations in
temperature (T).
These experiments relating light and
temperature were followed up by Herschell and formed the basis
for Max Planck’s quantum theory (1900). |
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William Frederick
Herschell 1738-1822 CE: Born in Hanover, Germany, William
Herschell was an English astronomer and telescope maker who discovered
the planet Uranus in 1781 and infrared solar “heat” rays in 1800.
Infrared radiation is commonly employed in auto-refractors for
determining the refractive error of the eye including myopia, hyperopia,
astigmatism, and higher-order aberrations.
The advantage of using
infrared lies in the facility to use electronic sensor-detectable safe
levels of radiation almost invisible to the human eye. Further, infrared
imaging of biological organs aids in medical diagnostics (thermography),
and infrared spectroscopy is used for biochemical investigations.
William
Herschell pioneered the study of binary stars and nebulae and
established the basic form of our Milky Way Galaxy. He was assisted by
his sister Caroline, and his work was continued after him by his son,
John F. W. Herschell. |
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Jean Baptiste
Joseph Fourier 1768-1830 CE: Born in Bourgogne, Fourier’s
education was interrupted during the French revolution and he decided to
accompany Napoleon on his Egyptian campaign. Based on his formulations
of heat flow in metallic objects (1807), Fourier proposed that any
mathematical function can be represented by trigonometric series.
In the 21st Century, Fourier analysis forms the basis for
calculations on the harmonic components of natural images and time
series data by vision scientists. Further, Fourier synthesis helps
create specific targets for visual psychophysics and neurophysiology
research. Modulation transfer in the eye and in any optical system can
be quantitatively described by a double integral function of a
trigonometric “Fourier” series. Fourier’s work laid the foundation for
dimensional analysis and linear programming. He also studied probability
and statistics. |
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| Johann Wilhelm
Ritter 1776-1810 CE: Born in Samnitz, Silesia (then in Prussia,
now Poland), Ritter was the German physicist who studied medicine at
Jena and discovered ultra-violet radiation. He also performed early
research on electrolytic cells. Ritter noted Hershell’s discovery in
1800 of “heat-rays” and was inspired to look for “cool-rays” at the
other end of the visible spectrum. Ritter noticed that silver chloride
was transformed faster from white to black when it was placed at the
dark violet-end of the solar spectrum. He termed these "chemical rays,"
later renamed ultraviolet radiation, used for biochemical skin tests
(e.g. carotenoid estimation), fluorescence, and other applications. |
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David Brewster
1781-1868 CE: Born in Jedburgh, Scotland, Brewster made
discoveries on diffraction and polarization of light and documented in
1815 that the polarization of a beam of reflected light is maximized
when the reflected and refracted rays are orthogonal to each other.
Further, the tangent of the angle of polarization is numerically equal
to the refractive index of the reflecting medium when polarization is
maximized.
Brewster invented the kaleidoscope in 1816 and was
knighted in 1831. His famous words from an 1830 publication (Quarterly
Review) include, “Science flatters no courtier, mingles in no political
strife.” Many retinal imaging devices utilize polarization of light as a
basis for their filtering and contrast-enhancement technologies. In the
eye, the cornea and the retinal nerve-fibre layers are known to alter the polarization
of incident light. |
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Augustin Jean Fresnel 1788-1827 CE: This
physicist and civil engineer, born in Broglie, Normandy, and
educated in Paris, refined the theory of polarized light by
proving in 1821 that light is a transverse wave.
He developed a
system of large concentric rings of triangular cross-section
that operated like a giant lens to produce a bright collimated
beam from a lighthouse to direct ships in the night.
Fresnel prisms and Fresnel lenses are currently widely employed
in optometric eye-care for patients with strabismus, and the
concept has been used in the design of intraocular lenses
surgically implanted after the removal of a cataractous biological lens from the eye.
Several brands of contact lens also employ such prismatic
“echelons” for selective focusing of near objects through the centre of the pupil.
The most recent laser techniques in the
21st Century for the surgical correction of presbyopia
(refractive surgery to help focus near objects on the retina),
rely on Fresnel echelons etched into the cornea by a femtosecond
laser suite. |
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George Biddell Airy 1801-1892 CE: Born in
Northumberland, Sir Airy studied mathematics at Cambridge where
he became professor of astronomy in 1828.
He installed a
telescope In Greenwich, England and measured Greenwich Mean Time
(made legal in 1880) by mapping the transit of stars across the
meridian.
By 1847 Sir Airy had devised an instrument for
calculating altitude and azimuth for mapping location in the
sky.
Such calculations are essential for mapping space as
it projects upon the centres of rotation of the eye, and for
specifying location on the retina, the cornea, and in the
concave bowl of a perimetry device for measuring visual field.
The intensity distribution in the image of a star-like object is
known as the “Airy disc”-- “maxima” and “minima” forming a point
spread function (PSF). |
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Conclusions
The design of optical instruments is an inter-disciplinary endeavour that has
received contributions from many machinists and engineers of the middle
ages. In addition, the fields of mathematics and biology meet when light
enters the eye and patterns in the image become biochemical reactions in
the retina. Here, biochemistry turns into cell biology as neural
impulses initiate psychological perception.
To review the history of
pre-modern optics in relation to current eye care technology has been my
attempt in this paper-- from the right-angled triangle (Pythagoras, c.
580- 500 BC) to the point-spread function (George Biddell Airy,
1801-1892). I hope I have succeeded to an acceptable degree.
Acknowledgements
I thank my mentors, colleagues,
students, collaborators, employees, advisors and investors.
Illustrations are from online world-wide web resources, and are not
known to be IP protected.
References
1. Hutchinson Dictionary of Scientists,
1996: Helicon Publishing Ltd., Oxford, UK; Editors S Jenkins-Jones, S
Karmali, T Ballsdon, I von Essen, C Thompson, K Young, A Farkas, J Webb,
A Dixon and T Caven.
2. The Physics Book: From the Big Bang
to Quantum Resurrection, 250 Milestones in the History of Physics, 2011;
Sterling Publishing Company, Inc., New York; Clifford A. Pickover
3. Wikipedia: The Free Encyclopedia.
http://en.wikipedia.org
4. The Science of Leonardo. Inside the
mind of the great genius of the Renaissance, 2007: Doubleday Broadway
Publishing Group, Random House Inc., New York; Fritjof Capra.
5.
Benjamin Franklin’s Science, 1996: Harvard University Press, Cambridge,
MA; I. Bernard Cohen. Adler’s Physiology of the Eye 8th and 11th
Edition, 1985, 2011: Saunders, Elsevier, Inc., New York. |
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