Holography in the context of Computer-generated hologram

Autostereoscopy is any method of displaying stereoscopic images (adding binocular perception of 3D depth) without the use of special headgear, glasses, something that affects vision, or anything for eyes on the part of the viewer. Because headgear is not required, it is also called "glasses-free 3D" or "glassesless 3D".

There are two broad approaches currently used to accommodate motion parallax and wider viewing angles: eye-tracking, and multiple views so that the display does not need to sense where the viewer's eyes are located. Examples of autostereoscopic displays technology include lenticular lens, parallax barrier, and integral imaging. Volumetric and holographic displays are also autostereoscopic, as they produce a different image to each eye, although some do make a distinction between those types of displays that create a vergence-accommodation conflict and those that do not.

Security holograms are labels with a hologram printed onto it for sale security reasons.

It is argued by the International Hologram Manufacturers Association that holograms on security labels are difficult to forge because they are replicated from a master hologram which requires expensive specialized and technologically advanced equipment. However, security holograms have also been criticised for their ineffectiveness, because equipment for manufacturing holograms has become significantly easier to access, and because few people have the expertise and equipment to authenticate them accurately.

In optics, a diffraction grating is a grating with a periodic structure of appropriate scale so as to diffract light, or another type of electromagnetic radiation, into several beams traveling in different directions (i.e., different diffraction angles) known as diffracted orders. The emerging coloration is a form of structural coloration. The directions or diffraction angles of these beams depend on the wave (light) incident angle to the diffraction grating, the spacing or periodic distance between adjacent diffracting elements (e.g., parallel slits for a transmission grating) on the grating, and the wavelength of the incident light. Because the grating acts as a dispersive element, diffraction gratings are commonly used in monochromators and spectrometers, but other applications are also possible such as optical encoders for high-precision motion control and wavefront measurement.

For typical applications, a reflective grating has ridges or "rulings" on its surface while a transmissive grating has transmissive or hollow slits on its surface. Such a grating modulates the amplitude of an incident wave to create a diffraction pattern. Some gratings modulate the phases of incident waves rather than the amplitude, and these types of gratings can be produced frequently by using holography.

In physics, coherence length is the propagation distance over which a coherent wave (e.g. an electromagnetic wave) maintains a specified degree of coherence. Wave interference is strong when the paths taken by all of the interfering waves differ by less than the coherence length. A wave with a longer coherence length is closer to a perfect sinusoidal wave. Coherence length is important in holography and telecommunications engineering.

This article focuses on the coherence of classical electromagnetic fields. In quantum mechanics, there is a mathematically analogous concept of the quantum coherence length of a wave function.