One-way mirror

Under a one-way mirror (also semi-transparent mirror, Venetian mirror, way mirror or police level ) is generally understood as an optical component (such as a glass plate ), reflects the incoming light on one side, but lets through non-mirrored on the other side. Thus, it is possible that one can observe, for example, people on the opposite side, while the opposite can only see his own reflection. A medium that brings such properties with it (but see optical isolator ) according to the current physical understanding is not possible. In order to receive glass panes with these properties, one uses a weakness of the human eye (or all optical recording devices ), namely that only a limited range of available brightness range can be detected, while other areas appear over - or underexposed.

Operation

A real one-way mirror is a float glass obtained by vacuum cathode sputtering (sputtering ) was coated with a thin metal oxide layer. In contrast to a real mirror, this layer is thin enough to transmit can also be parts of the incident light. Thus, only a certain proportion of the light is reflected, and the rest passes to the other side. This beam-splitting property does not possess normal glass plates such as window panes, but in the necessary ratio of reflection and transmission.

One-way mirror, the application is the actual one-sided, optical shielding of a room, have a very low light transmittance and a strong light reflection, so let hardly any light to the other side through. This automatically initiates the conditions that must prevail in order for a one-way mirror works as intended:

• The monitored space shall be very brightly lit, so that sufficient light reaches the other side. But this means at the same time that much light is reflected back. Persons in the monitored space so see mainly their reflection.

• On the observational side, this effect has to be minimized, because the observer will not possible to perceive his own reflection. Therefore, the space of the observer must be as little as possible illuminated, so that little light is reflected. This of course gets even less light to the monitored space, yielding the quasi observer can no longer recognize from there.

The lighting situation thus requires the two crucial effects that ensure that the observer can not be seen, on the one hand the little light that comes from the observer, and on the other hand, the large amounts of light that are reflected by the one-way mirror and dazzle the observer.

DC Brightly lit rooms

Also equally bright rooms can be effectively hidden from view: One uses a partially transparent mirror film on a substrate made ​​of colored glass, which may, on the mirror side facing away additionally carries an anti-reflective coating. While the light has to pass through the control room there looking teilabsorbierende glass twice ( before and after the reflection ), this is only once the case for the light passing from the other room through the mirror layer light. Thus the disc from the control room appears dark and obstructs the view less. The light in the space to be observed, however, largely reflected by the mirror layer located on this page - the area appears bright contours in the control room are outshone.

Application

One-way mirrors are now mounted in many supermarket outlets on the wall, so that the store manager can monitor from his office to the checkout area, but does not allow others to take with him a full view.

The police also uses them to enable victims in a confrontation to identify a perpetrator undetected. Video cameras that map a camera image on a monitor, but becoming more widespread.

On the basis of such a mirror and using the lighting conditions change individual effects are realized on ghost trains like.