Ibn al-Haytham

Ibn al-Haytham, Latinized as Alhazen (c. 965 – c. 1040), was a mathematician, astronomer, and physicist of the Islamic Golden Age from present-day Iraq. Referred to as "the father of modern optics", he made significant contributions to the principles of optics and visual perception in particular. His most influential work is titled Kitāb al-Manāẓir (Arabic: كتاب المناظر, 'Book of Optics'), written during 1011–1021, which survived in a Latin edition. The works of Alhazen were frequently cited during the Scientific Revolution by Galileo Galilei, René Descartes, Johannes Kepler, and Christiaan Huygens.

Ibn al-Haytham was the first to correctly prove vision as intromissive rather than extramissive, and to argue that vision occurs in the brain, pointing to observations that it is subjective and affected by personal experience. He also stated a principle of least time for refraction, similar to the results of the much later results from Fermat's principle. He made major contributions to catoptrics and dioptrics by studying reflection, refraction and nature of images formed by light rays. He was the first physicist to give a complete statement of the law of reflection, and was also the first to describe the horopter, spherical aberration, color constancy, and unconscious inference. Ibn al-Haytham was an early proponent of the concept that a hypothesis must be supported by experiments based on confirmable procedures or mathematical reasoning – an early pioneer in the scientific method five centuries before Renaissance scientists, he is sometimes described as the world's "first true scientist". He was also a polymath, writing on philosophy, theology and medicine.