Dichroic and Color Filters

Color glass filters (color filters) are characterized by a selective absorption in specific optical wavelength ranges. The filtering effect is caused by the properties of the selected filter glass. If the filtering effect is in the visible spectrum of light, then the colored glass filter appears colored.
Dichroic filter is a thin-film interferometric filter which passes narrow range of wavelengths, e.g. a specific color.
Color filters properties can be further modified by adding dichroic filters, i.e. thin film dielectric coatings. Such filters combine absorption effects of a color glass with reflection effects of interference layers, giving specific advantages.
Such filters are designed on the basis of standard color glasses set produced by SHOTT. Several kinds of glasses can be applied to one filter in order to fulfill any requirements.
Solaris Optics produces custom color glass filters and dichroic filters in its premises in Poland.

Colored glass filter properties

Main properties of colored glass filters are spectral transmittance and spectral internal transmittance.
Spectral transmittance τ(λ) is defined as a ratio of the transmitted spectral flux to the incident spectral flux. Hence spectral transmittance includes glass absorption as well as reflection losses on filters’ front and rear surfaces.
Filter spectral transmittance:

Spectral internal transmittance τi(λ) describes only the filter glass absorption, not considering the reflection losses. It is a ratio of the leaving spectral flux (before the light hits the rear side) to the entering spectral flux (after the filter front surface).
Filter spectral internal transmittance:

Technical data of colored glass and dichroic filters

Standard specifications of color glass filters produced by Solaris Optics:

  • Substrate material: according to customer requirements
  • Dimensions (side length, diameter): 4 to 150 mm
  • Dimension tolerance: -0.1 mm
  • Clear aperture (active area): 90%
  • Thickness tolerance: ±0.2 mm
  • Flatness (633 nm) 2 λ per inch
  • Surface quality (scratch – dig) 60 – 40
  • Parallelism <15 arcmin
  • Coating: according to customer requirements

The filters can be also manufactured also in higher quality levels, e.g. 40 – 20, λ/10 (633 nm), parallelism 1 – 3 arcsec.

Applications of colored glass filters

Color glass filters are oftentimes a cost-effective filtering option. They find applications in measurement, instrumentation, medical treatment, education, lighting, military, etc.
Should you have questions regarding your application of color glass or dichroic filters, please do not hesitate to contact us!
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