An optical sight, also known as a scope, is an optical aiming device. Its origins can be traced back to the ancient aiming device "Wangshan" mentioned in Shen Kuo's *Dream Pool Essays* from the Northern Song Dynasty. Documentary records of telescopic low-light aiming devices exist from before the 19th century. In the early 20th century, optical sights with practical combat value emerged and gained prominence during World War I.
Sights are mainly divided into four categories: telescopic, collimating, reflecting, and laser sights. Telescopic sights form a real image of the target through an objective lens, suitable for distant static targets; collimating sights (including those with an inner red-green dot) utilize the principle of binocular image overlap, suitable for close-range moving targets; reflecting sights use a lens group to reflect images, enabling aiming at moving targets; laser sights use a visible laser beam to assist aiming. Modern developments include variable magnification designs, the Binden aiming concept (automatic magnification adjustment), and holographic sights (using the principle of light diffraction). The Israeli SMASH2000 smart sight features laser rangefinding, target locking, and image recording and transmission capabilities, while the US military's XM157 integrates a ballistic computer and a laser rangefinder. Night vision sights incorporate low-light enhancement and infrared thermal imaging technologies, enabling target identification in dark environments.
