-Beam splitter - mirror and prism system capable of partly reflecting, partly transmitting light.
Beam splitter (semitransparent mirror)
Light-gathering window
Framelines projection/parallax compensation unit
Framelines projection semitransparent mirror
Rotating mirror/pentaprism
Viewfinder
Viewfinder frame
Static Image
Secondary Image ...
Beam Splitter-An optical device within a color camera that splits the white light into three primary colors: red, green, and blue. Camcorder-A portable video camera with videotape recorder (VTR) and a microphone attached to form a single unit.
The system utilizes a beam splitter (implemented as a small semi-transparent area of the main reflex mirror, coupled with a small secondary mirror) to direct light to an AF sensor at the bottom of the camera.
This can cause problems with cameras that use a beam splitter to lead some of the light towards the AF sensors and metering cells. These beam splitters also act like a polarizer.
Inside most modern cameras is a beam splitter that directs some light to the viewfinder and some to the meter. Based on how it functions, the light that reaches the meter is effectively polarized by the beam splitter.
A beam splitter directs light to the different sensors. Think of the light entering the camera as water flowing through a pipe. Using a beam splitter would be like dividing an identical amount of water into three different pipes.
Having removed the effect of linear polarization, the light functions normally inside the camera, in the beam splitter, and reaching the autofocus and metering sensors properly.
For fast sequence shooting and to reduce vibrations, some SLR optical systems use a beam splitter (prism) instead of the quick return swinging mirror. The picture seen through the viewfinder is almost 100% identical to the resulting photo.
 See also: Light, Lens, Camera, Image, Focus
  
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