Beam splitter

After the optical glass surface is plated with a layer or multilayer film, a part of the light is reflected and the other part of the light is refracted, and the beam is divided into two beams, that is, beam splitting is realized.

The beam splitter mirror is mainly used to divide the incident beam into two beams with a certain light intensity ratio, transmission and reflection. There are two types of fixed beam splitter mirror and variable beam splitter mirror. The variable beam splitter and beam mirror are divided into steps and continuous transient changes.

The beam splitter is usually used at an Angle, and it can easily separate the incident light into reflected light and transmitted light. If the reflected light and transmitted light have different spectral components, or have different colors, the beam splitting mirror is usually called a dichroic mirror. If a beam of light is divided into two beams of the same spectral composition, that is, in a certain wavelength region, such as visible light, the same transmittance and reflectivity ratio for each wavelength, so the reflected light and transmitted light are neutral, this beam splitter is called a neutral beam splitter. A neutral beam splitter with a 50/50 transmission to reflection ratio is most commonly used.

The commonly used neutral beam splitter mirror has two structures, one is to plate the film layer on a transparent plate, the other is to plate the film layer on a 45° right Angle prism slope, and then glue a prism of the same shape to form a glued cube. Plate beam splitter, due to the inevitable astigmatism, is usually used in medium and low optical devices. For optical systems with high performance requirements, prism beam splitter mirrors can be used. The advantage of glued cube beam splitter mirror (also known as splitter prism) is that it is convenient to be installed in the instrument, and because the film layer is not exposed to air, it is not easy to damage and corrosion, so the mechanical and chemical stability of the film material is low. But the positive bias effect of glued cube beam splitter is also obvious.

Films or film combinations with almost constant reflectance in a certain wavelength region can play the role of neutral beam splitting. Metal beam splitter and medium beam splitter are commonly used.