Divider mirror

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A splitter mirror (or partially transparent mirror ) is a mirror that reflects part of the incident light and transmits the other part . The one-way mirror is related to this .

It usually consists of a dielectric layer system on one side and possibly a reflection-reducing coating on the other side (to avoid double images). Instead of the dielectric layer system, for example, a very thin metal coating can also be used.

This method is used for the neutral and low-absorption division of light in lasers , in optical measurement technology or in television applications (e.g. teleprompter ).

Display and overlay systems

In the TV sector, such splitter mirrors were and are often used as a simple way of realizing trick effects with relatively limited effort. A screen pointing upwards is aimed at an inclined mirror surface that guides the TV image to a camera or a viewer. The image on the screen is essentially dark. On the horizontal main axis of the viewer, behind the mirror, there is a mostly miniaturized scene, over which the bright parts of the screen are blinded, so to speak. In the case of presentations in front of an audience, the result appears as if a flat image was standing freely in the space behind the mirror. If the object is not particularly large, it is usually not consciously noticed that it is just a flat representation in a 3D scene.

With a variant of this structure, Ridley Scott used the normally undesirable red-eye effect for the film Blade Runner in order to make the actors' pupils glow. The camera filmed through a semi-transparent mirror, which directed the light of a lamp attached to the side into the eyes of the actors. The brightness of this lamp could be regulated, and since even low light intensities were sufficient for this effect, the recorded image was not unnecessarily brightened.

In a particularly large version of the arrangement, an artist used this method to create a double-sided video illusion for the Danish Design Center, which is built around a real, but empty, oblong dining table. According to a random pattern, food becomes visible and disappears again, e.g. B. Apples that are conjured up on plates, or milk that flows from an invisible jug into one of the glasses. In addition to various oversized fruits appearing in the room, a life-size, moving domestic pig can also be found in the concept. The arrangement suggests that here the mirrors are arranged in such a way that the screens or, alternatively, the projection surface of the projectors used is arranged above the viewer's height. The same applies to pyramid-like devices for presentation purposes from the manufacturer RealFiction, which is involved in the project. A manufacturer called Cheoptics, on the other hand, turns the pyramid upside down, making its presentations accessible from all sides. There are a few more roughly comparable systems on the market that are often offered there under the incorrect category name “holographic display”. True holographic screens are also known for a flat image, but use fine lenses to display the actual image very closely parallel to the optically active element.

More recently, even very large-format mirror systems based on special foils have been implemented. This requires a considerable amount of space between the audience and the stage. The special effect is that you can apparently unite people next to each other on a stage, part of which is actually in the room while the other part could possibly be at the other end of the world via a mostly digital feed and is filmed there. The image is usually projected onto a screen surface on the floor in the area of ​​the so-called orchestra pit with one or more projectors. As a side effect, it is even possible to play information from a teleprompter on the ceiling above, which can then only be read by the people actually present on the stage. A minor limitation is that the image of the faded in people mostly slowly becomes weaker in the area of ​​the soles of the feet. Furthermore, a more or less sharp break in the representation can also be expected on the sides of the stage. According to reports, the method is intended to be used in cases of strong air movements, e.g. B. by loud music, lead to a rather moderate, mostly blurred image.

The method is currently used sporadically in public, e.g. B. at fashion shows. The possibility of using them without a stored real image and instead having the entire scenery from real film and other image material generated in a computer system is sometimes practiced. The concert-goer is presented with an empty stage, which, like in the cinema, is only filled by playing or importing video material.

See also

Web links

Individual evidence

  1. ↑ Film commentary by Ridley Scott, Blade Runner (Final Cut) 2007