Optical Filters—Dichroic Mirrors/Dichroic Beamsplitters

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What are dichroic mirrors?

Dichroic mirrors known as cold mirrors are commonly used behind a light source to reflect visible light while allowing the invisible infrared light to pass through.

Dichroic mirrors are typically used at AOI 45 degrees. There are short-pass and long-pass mirrors.

  • A shortpass mirror is one which has a high transmittance at short wavelengths and high reflectance at longer wavelengths.
  • A longpass mirror is one which has high reflectance at short wavelengths and high transmittance at longer wavelengths.

Here is a spectrum of long-pass dichroic mirror:

What specifications are required for a dichroic mirror(dichroic beamsplitter):

  • Reflective wavelengths range
  • Transmittance wavelengths range
  • Edge wavelength

Applications of dichroic mirrors:

  • In fluorescence microscopy, dichroic filters/dichroic mirrors are used as beam splitters to direct illumination of an excitation frequency toward to the sample and then pass a particular emission frequency.
  • Some LCD projectors use dichroic filters instead of prisms to split the white light from the lamp into the three colours before passing it through the three LCD units.
  • Dichroic filters/dichroic mirrors, excitation filters and emission filters form the fluorescence filter set used in fluorescence microscopy.

Dichroic filters/ Dichroic mirrors at Optolong Optics:

  • IAD hard coating
  • Wavelengths range from UV to infrared
  • High reflectance
  • High transmittance
  • Surface quality 40/20, 60/40
  • High precision polished glass substrates
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