 In the 10th century Yu Chao-Lung supposedly projected images of pagoda models through a small hole onto a screen to study directions and divergence of rays of light.Arab physicist Ibn al-Haytham (known in the West by the Latinised Alhazen) (965–1039) extensively studied the camera obscura phenomenon in the early 11th century.He provided the first competent geometrical and quantitative descriptions of the phenomenon and must have understood the relationship between the focal point and the pinhole,

In his "Book of Optics" (circa 1027), Ibn al-Haytham explained that rays of light travel in straight lines and are distinguished by the body that reflected the rays, and then wrote