Ibn al-Haytham, Father of Optics: An Optician, Optometrist 

and OphthalmologistDr. Abdul Latif

Department of Ilmul AdivaFaculty of Unani Medicine, AMU,Aligarh

abdullatifamu@gmail.com

The International Year of Light 2015 (IYL2015), has been started and announced by UNESCO in Paris

• IBN AL-HAYTHAM TO BE THE FOCUS OF THE INTERNATIONAL YEAR OF LIGHT 2015

• UNESCO and the International Year of Light 2015 partners with 1001 Inventions for 2015 campaign for Ibn Al-Haytham

• The International Year of Light and Light-based Technologies (IYL2015) is delighted to welcome as Founding Partner the award-winning educational organization 1001 Inventions. British-based 1001 Inventions has the specific mission to raise awareness of the contributions to science, technology and culture from the Golden Age of Muslim Civilization, and will play a key role during IYL2015 to promote and celebrate the 10th century pioneer Ibn Al-Haytham. Ibn Al-Haytham’s seminal work on optics Kitab al-Manazir (The Book of Optics) was written around 1015, and its 1000th anniversary is listed openly in the United Nations resolution on IYL2015 as a focal point of celebration.

UNESCO announces partnership with 1001 Inventions to celebrate                    

Ibn Al-Haytham 

Director-General Irina Bokova announces UNESCO's partnership with 1001 Inventions to launch a global campaign to celebrate the 10th century scientist Ibn Al-Haytham. The campaign called "1001 Inventions and the World of Ibn Al-Haytham" will be part of the UNESCO led International Year of Light 2015.

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Anyone who has ever used vision glasses or contact lenses, taken a picture with a camera or watched television has a reason to be thankful to the Father of Optics, Al-Haytham

Ibn al Haytham

Abu Ali al-Hasan Ibn-al-Haytham known was born in 965 CE in Basra (Iraq); also known as Al-Basri. He received his education in Basra and Baghdad and later traveled to Egypt and Spain and died in 1040 possibly in Cairo, Egypt. He was also one of the most eminent physicist’s who ever lived. Along with that he is also famous Mathematician, and astronomer.

Known in the West as Alhazen, Alhacen, or Alhazeni, Ibn al-Haytham was the first person to test hypotheses with verifiable experiments, developing the scientific method more than 200 years before European scholars learned of it—by reading his books.Ibn al-Haytham is regarded as the “father of modern optics” for his influential Book of Optics (Kitâb al-Manâzir ) and his extensive contribution in the field of optics.

In his massive study of light and vision, Kitâb al-Manâzir (Book of Optics ), Ibn al-Haytham submitted every hypothesis to a physical test or mathematical proof.Besides the Book of Optics, Ibn al-Haytham wrote several other treatises on optics.His Risala fi l-Daw’ (Treatise on Light) is a supplement to his Kitab al-Manazir (Book of Optics). The text contained further investigations on the properties of luminance and its radiant dispersion through various transparent and translucent media.He also carried out further examinations into anatomy of the eye and illusions in visual perception.

Ibn al-Haytham also gave the first clear description and correct analysis of the camera obscura and pinhole camera and built the world's first camera obscura.While Aristotle, Theon of Alexandria(335-405), Al-Kindi(801-873) and Chinese philosopher Mozi(470-391 B.C.) had earlier described the effects of a single light passing through a pinhole, none of them suggested that,what is being projected onto the screen is an image of everything on the other side of the aperture.Ibn al-Haytham was the first to demonstrate this with his lamp experiment where several different light sources are arranged across a large area. He was thus the first to successfully project an entire image from outdoors onto a screen indoors with the camera obscura.

Two major theories on vision prevailed in classical antiquity.The first theory, the emission theory, was supported by such thinkers as Euclid(323-283 B.C.) and Ptolemy(90-168), who believed that sight worked by the eye emitting rays of light.The second theory, the intromission theory supported by Aristotle(384-322 B.C.) and his followers, had physical forms entering the eye from an object.Ibn al-Haytham argued that the process of vision occurs neither by rays emitted from the eye, nor through physical forms entering it.He instead developed a highly successful theory which explained the process of vision as rays of light proceeding to the eye from each point on an object, which he proved through the use of experimentation.

Lens (c.984)Ibn al-Haytham’s treatise established optical science.

The earlier lenses were made of circular pieces of rock crystal or semiprecious stone, such as beryl and quartz, which were ground and polished so that they produced a magnified image when looked through. The oldest known lens artifact was one made of rock crystal dating from around 640 B.C.E. and excavated in Nineveh, near the modern city of Mosul, Iraq. The most common form was circular and thicker in the middle than around the edge, and having both its front and back surfaces the same shape.

The modern convex lens developed from the ancient Greek burning glass. Here a spherical vase of water would be used to concentrate the rays of the sun onto a small area, which heated up. The heat was used to ignite fires in temples or to cauterized wounds.

The Iraqi mathematician and optics engineer Ibn Sahl (c. 940-1000) wrote the treatise On Burning Mirrors and Lenses (984) in which he set out his understanding of how curved mirrors and lenses bend and focus light, using what is now known as Snell’s law to calculate the shape of lenses. But the Iraqi Ibn al Haytham (965-1039), also known as Alhazen, is regarded as “the father of optics” for his treatise, the Book of Optics, (1011-1021), in which he proved that rays of light travel in straight lines, explained hoe the lens in the human eye forms an image on the retina, and described experiments with a pin hole camera.

In the thirteen century convex lenses were used in spectacles to correct farsightedness. The use of concave lenses, which disperse the light as opposed to concentrating it, to correct for farsightedness, came in the early fifteen century. DH

 GLASS, TELESCOPE, MICROSCOPE, SPECTACLES,

BIFOLCALS, EYE TEST, SPECTROSCOPE, CONTACT LENSES.

Refractive Errors

Refractive errors often are the main reason a person seeks the services of an optician ,optometrist or ophthalmologist. But what does it really mean when we're told that our vision is blurry because we have a refractive error?We see the world around us because of the way our eyes bend (refract) light. Refractive errors are optical imperfections that prevent the eye from properly focusing light, causing blurred vision. The primary refractive errors are nearsightedness, farsightedness and astigmatism.Refractive errors usually can be "corrected" with eyeglasses or contact lenses, or they can be permanently treated with LASIK and other vision correction surgery (also called refractive surgery).

How  Light  Travels  Through the Eye

In order to see, we must have light. While we don't fully understand all the different properties of light, we do have an idea of how light travels.A light ray can be deflected, reflected, bent or absorbed, depending on the different substances it encounters.

Watch this video on what causes blurry vision and how we can correct it

When light travels through water or a lens, for example, its path is bent or refracted. Certain eye structures have refractive properties similar to water or lenses and can bend light rays into a precise point of focus essential for sharp vision.Most refraction in the eye occurs when light rays travel through the curved, clear front surface of the eye (cornea). The eye's natural (crystalline) lens also bends light rays. Even the eye's tear film and internal fluids (aqueous humor and vitreous) have refractive abilities.

How the Eye Sees

The process of vision begins when light rays that reflect off objects and travel through the eye's optical system are refracted and focused into a point of sharp focus.For good vision, this focus point must be on the retina. The retina is the tissue that lines the inside of the back of the eye, where light-sensitive cells (photoreceptors) capture images in much the same way that film in a camera does when exposed to light. These images then are transmitted through the eye's optic nerve to the brain for interpretation.Just as a camera's aperture (called the diaphragm) is used to adjust the amount of light needed to expose film in just the right way, the eye's pupil widens or constricts to control the amount of light that reaches the retina.In dark conditions, the pupil widens. In bright conditions, the pupil constricts.

Causes of Refractive Errors

The eye's ability to refract or focus light sharply on the retina primarily is based on three eye anatomy features: 1) the overall length of the eye, 2) the curvature of the cornea and 3) the curvature of the lens inside the eye.•Eye length. If the eye is too long, light is focused before it reaches the retina, causing nearsightedness. If the eye is too short, light is not focused by the time it reaches the retina. This causes farsightedness or hyperopia.•Curvature of the cornea. If the cornea is not perfectly spherical, then the image is refracted or focused irregularly to create a condition called astigmatism. A person can be nearsighted or farsighted with or without astigmatism.•Curvature of the lens. If the lens is too steeply curved in relation to the length of the eye and the curvature of the cornea, this causes nearsightedness. If the lens is too flat, the result is farsightedness.More obscure vision errors, known as higher-order aberrations, also are related to flaws in the way light rays are refracted as they travel through the eye's optical system.These types of vision errors, which can create problems such as poor contrast sensitivity, are detected through new technology known as wave front analysis.

Detection  and  Treatment  of Refractive ErrorsYour eye doctor determines the type and degree of refractive error you have by performing a test called a refraction.This can be done with a computerized instrument (automated refraction) or with a mechanical instrument called a phoropter that allows your eye doctor to show you one lens at a time (manual refraction).Often, an automated refraction will be performed by a member of the doctor's staff, and then the eye care practitioner will refine and verify the results with a manual refraction.Your refraction may reveal that you have more than one type of refractive error. Contd…

For example, your blurred vision may be due to both nearsighted and astigmatism.Your eye doctor will use the results of your refraction to determine your eyeglasses prescription. A refraction, however, does not provide sufficient information to write a contact lens prescription, which requires a contact lens fitting.Eyeglass lenses and contact lenses are fabricated with precise curves to refract light to the degree necessary to compensate for refractive errors and bring light to a sharp focus on the retina.Vision correction surgeries such as LASIK aim to correct refractive errors by changing the shape of the cornea, so that light rays are bent into a more accurate point of focus.

An eye care practitioner performs a manual refraction.(Image: National Eye Institute)

ConclusionHis theory of vision is basis of all optical requirement

Thanks to Ibn al haytham