Thin Film Glossary
19Sep
- Angle of Incidence (AOI)
- The angle at which a filter is tilted relative to the primary ray. For example, an AOI of 0° means the primary ray is perpendicular to the plane of the filter.
- Bandpass Filter
- A filter that transmits a band of wavelengths while blocking the wavelengths on either side of the passband.
- Blocking
- The level of rejection of light outside the passband.
- Borofloat® (Borosilicate Glass)
- A high temperature substrate material with high chemical resistivity against water, neutral, acidic and saline solutions.
- Center Wavelength (CWL)
- The center of the passband for a bandpass filter. Another common definition is the average of the 50% of peak of each edge of a bandpass filter.
- Cone Angle
- The range of angles of light incident on the filter about the AOI.
- Cone Angle Average
- Average of transmission or reflection across the cone angle
- Dichroic
- A filter that transmits one band and reflects a different band
- Edge Filter
- A filter that transmits a band of wavelengths and blocks only low side (long wave pass) or high side (shortwave pass) of wavelengths.
- Fused Silica
- Substrate material composed of amorphous silicon dioxide.
- Long Wave Pass (LWP)
- An edge-type filter that transmits longer wavelengths and blocks shorter wavelengths.
- Notch Filter
- A filter that blocks a narrow range while transmitting wavelengths on either side of the blocked wavelength range.
- Optical Density (OD)
- The negative logarithm (base 10) of transmittance (T). (T on a zero to unity scale)
- Passband
- The range of wavelengths that are desired to be transmitted.
- Parallelism
- The orientation tolerance allowed between a feature of interest and a reference datum. For plano-plano optical filters, the term describes how parallel the two main surfaces of the optic are to one another.
- Ripple
- Variations in transmission in the passband.
- Shortwave Pass (SWP)
- An edge-type filter that transmits the shorter wavelengths and blocks higher wavelengths.
- Spectral Slope
- Rate of change of the spectrum from a passband to a blocking band.
- Transmitted Wavefront Error (TWE)
- Distortion of the wavefront of a plane wave as it transmits through a filter, generally given in units of the HeNe wavelength of 633nm.
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