The Book of Optics (Arabic: كتاب المناظر, romanized: Kitāb al-Manāẓir; Latin: De Aspectibus or Perspectiva; Italian: Deli Aspecti) is a seven-volume treatise on optics and other fields of study composed by the medieval Arab scholar Ibn al-Haytham, known in the West as Alhazen or Alhacen (965–c.

[2]: 60–67 [3][4][a][b] The book is also noted for its early use of the scientific method, its description of the camera obscura, and its formulation of Alhazen's problem.

The extramission or emission theory was forwarded by the mathematicians Euclid[6] and Ptolemy,[7] who asserted that certain forms of radiation are emitted from the eyes onto the object which is being seen.

An early version of the intromission theory, held by the followers of Aristotle and Galen, argued that sight was caused by agents, which were transmitted to the eyes from either the object or from its surroundings.

Al-Haytham offered many reasons against the extramission theory, pointing to the fact that eyes can be damaged by looking directly at bright lights, such as the sun.

[8]: 313–314  He wrote of the low probability that the eye can fill the entirety of space as soon as the eyelids are opened as an observer looks up into the night sky.

He also wrote that color acts much like light, being a distinct quality of a form and travelling from every point on an object in straight lines.

This idea presented a problem for al-Haytham and his predecessors, as if this was the case, the rays received by the eye from every point on the object would cause a blurred image.