Telescopic sight in the context of "Zoom lens"

Leica Camera AG (/ˈlaɪkə/) is a German company that manufactures cameras, optical lenses, photographic lenses, binoculars, and rifle scopes. The company was founded by Ernst Leitz in 1869 (Ernst Leitz Wetzlar), in Wetzlar, Germany. The name Leica is derived from the first three letters of the founder's surname (Leitz) and the first two of the word camera: lei-ca (LEItz CAmera).

In 1986, the Leitz company changed its name to Leica and moved its factory from Wetzlar to the nearby town of Solms.

An optical axis is an imaginary line that passes through the geometrical center of an optical system such as a camera lens, microscope or telescopic sight. Lens elements often have rotational symmetry about the axis.

The optical axis defines the path along which light propagates through the system, up to first approximation. For a system composed of simple lenses and mirrors, the axis passes through the center of curvature of each surface, and coincides with the axis of rotational symmetry. The optical axis is often coincident with the system's mechanical axis, but not always, as in the case of off-axis optical systems.

A sight or sighting device is any device used to assist in precise visual alignment (i.e. aiming) of weapons, surveying instruments, aircraft equipment, optical illumination equipment or larger optical instruments with the intended target. Sights can be a simple set or system of physical markers that serve as visual references for directly aligning the user's line of sight with the target (such as iron sights on firearms), or optical instruments that provide an optically enhanced—often magnified—target image aligned in the same focus with an aiming point (e.g. telescopic, reflector and holographic sights). There are also sights that actively project an illuminated point of aim (a.k.a. "hot spot") onto the target itself so it can be observed by anyone with a direct view, such as laser sights and infrared illuminators on some night vision devices, as well as augmented or even virtual reality-enabled digital cameras ("smart scopes") with software algorithms that produce digitally enhanced target images.

A sniper rifle is a high-precision, long-range rifle. Requirements include high accuracy, reliability, mobility, concealment, and optics, for anti-personnel, anti-materiel and surveillance uses by military snipers. The modern sniper rifle is a portable shoulder-fired rifle with either a bolt action or semi-automatic action, fitted with a telescopic sight for extreme accuracy and chambered for a high-ballistic performance centerfire cartridge.

Shooter video games, or shooters, are a subgenre of action video games where the focus is on the defeat of the character's enemies using ranged weapons given to the player. Usually these weapons are firearms or some other long-range weapons, and can be used in combination with other tools such as grenades for indirect offense, armor for additional defense, or accessories such as telescopic sights to modify the behavior of the weapons. A common resource found in many shooter games is ammunition, armor or health, or upgrades which augment the player character's weapons.

Shooter games test the player's spatial awareness, reflexes, and speed in both isolated single player or networked multiplayer environments. Shooter games encompass many subgenres that have the commonality of focusing on the actions of the avatar engaging in combat with a weapon against both code-driven NPC enemies or other avatars controlled by other players.

A monocular is a compact refracting telescope used to magnify images of distant objects, typically using an optical prism to ensure an erect image, instead of using relay lenses like most telescopic sights. The volume and weight of a monocular are typically less than half of a pair of binoculars with similar optical properties, making it more portable and also less expensive. This is because binoculars are essentially a pair of monoculars packed together — one for each eye. As a result, monoculars only produce two-dimensional images, while binoculars can use two parallaxed images (each for one eye) to produce binocular vision, which allows stereopsis and depth perception.

Monoculars are ideally suited to those applications where three-dimensional perception is not needed, or where compactness and low weight are important (e.g. hiking). Monoculars are also sometimes preferred where difficulties occur using both eyes through binoculars due to significant eyesight variation (e.g. strabismus, anisometropia or astigmatism) or unilateral visual impairment (due to amblyopia, cataract or corneal ulceration).

A night-vision device (NVD), also known as a night optical/observation device (NOD) or night-vision goggle (NVG), is an optoelectronic device that allows visualization of images in low levels of light, improving the user's night vision.

The device enhances ambient visible light and converts near-infrared light into visible light which can then be seen by humans; this is known as I (image intensification). By comparison, viewing of infrared thermal radiation is referred to as thermal imaging and operates in a different section of the infrared spectrum.

A sniper is a military or paramilitary marksman who engages targets from positions of concealment or at distances exceeding the target's detection capabilities. Snipers generally have specialized training and are equipped with telescopic sights. Modern snipers use high-precision rifles and high-magnification optics. They often also serve as scouts or observers feeding tactical information back to their units or command headquarters.

In addition to long-range and high-grade marksmanship, military snipers are trained in a variety of special operation techniques: detection, stalking, target range estimation methods, camouflage, tracking, bushcraft, field craft, infiltration, special reconnaissance and observation, surveillance and target acquisition. Snipers need to have complete control of their bodies and senses in order to be effective. They also need to have the skill set to use data from their scope and monitors to adjust their aim to hit targets that are extremely far away. In training, snipers are given charts to ensure they can make last-minute calculations in the field.