Infrared cut-off filter

The term infrared filter entirely different filter characteristics are referred to:

Infrared transmitting filter

In infrared photography, in infrared lights and receivers for infrared remote control and light barriers, an infrared filter serves largely or wholly filter out or absorb visible light. These filters are made of glass or plastic.

Infrared -blocking filter

Front of the image sensor of digital cameras and video cameras is typically an infrared cut filter (also infrared filter, " IR-cut ", " Hotmirror "), which is intended to avoid the incidence of infrared light. So that disturbing influences, the IR radiation can be avoided in the image quality of the sensor. This may be blurring or color distortion. These filters are interference filters and dichroic filters.

In headlights and projectors are often used filter glasses to (especially bulbs) to reduce the radiation of the lamps in the infrared, thus reducing the heating of the illuminated objects ( slide, film, speakers). These are also IR-cut filter, they are called here a heat protection filter.

Particularly easy to implement is a " water filter ", a rectangular water-filled cuvette in which the light passes through a minimum of 1 cm thick water layer. Such filters have been used in the past to reduce the strong IR portion of the light from a carbon arc lamp. The thermal stability is considerably larger than in thin film filters. In the picture you can also see that the extinction coefficient of water in the IR region more than a thousand times higher than in the visible range. See also: Eigenschaften_des_Wassers # Absorptionsverhalten_und_Farbe

Dichroic infrared filter

By dichroic filter layers (interference filter) on the glass envelope of incandescent lamps ( IRC halogen bulbs) is to increase the light yield by the infrared portion is reflected back to the filament selectively succeed. Since the filter also the long-wavelength ( red ) part of the visible spectrum somewhat limit, thereby increasing the color temperature. These coatings represent an infrared cut filter

The shield of dichroic lamps, wearing a dichroic infrared filter, which reflects only the visible spectral component. The sequence is also an increased color temperature of the emitted light, and a lower heating effect in the light beam, since the infrared portion of the bulb through the dichroic reflector escapes backward.

• Optical filter