A
parallax barrier is a device placed in front of an image source, such as a
liquid crystal display, to allow it to show a
stereoscopic image or
multiscopic image without the need for the viewer to wear 3D glasses. Placed in front of the normal LCD, it consists of a layer of material with a series of precision slits, allowing each eye to see a different set of
pixels, so creating a sense of depth through
parallax in an effect similar to what
lenticular printing produces for printed products and
lenticular lenses for other displays. A disadvantage of the technology is that the viewer must be positioned in a well-defined spot to experience the 3D effect. Another disadvantage is that the effective horizontal pixel count viewable for each eye is reduced by one half; however, there is research attempting to improve these limitations.