Ibn al-Haytham was an Arab mathematician, astronomer, and physicist.
Ibn al-Haytham was the first to explain that vision occurs when light bounces on an object and then is directed to one's eyes. And he was the first to point out that vision occurs in the brain, rather than in the eyes. He was also an early proponent of the concept that a hypothesis must be proved by experiments based on confirmable procedures or mathematical evidence—hence understanding the scientific method five centuries before Renaissance scientists.
Hasan Ibn al-Haytham was an Arab mathematician, astronomer, and physicist of the Islamic Golden Age. Sometimes called "the father of modern optics", he made significant contributions to the principles of optics and visual perception in particular, his most influential work being his Kitāb al-Manāẓir (كتاب المناظر, "Book of Optics"), written during 1011–1021, which survived in the Latin edition. A polymath, he also wrote on philosophy, theology and medicine.
His work on catoptrics in Book V of the Book of Optics contains a discussion of what is now known as Alhazen's problem, first formulated by Ptolemy in 150 AD. It comprises drawing lines from two points in the plane of a circle meeting at a point on the circumference and making equal angles with the normal at that point.