Angle of Incidence (AOI): The Angle of Incidence (AOI) is the designed angle in degrees at which the filter should be used, with a tolerance defining the range over which the filters other optical specifications (transmission band, blocking band etc) are still met.
Cone Half-Angle: The cone half-angle (CHA) refers to the allowable angular range over which photons can fall incident on a filter while maintaining the specified spectral performance. It is the angular range measured from the Angle of Incidence to the largest cone angle.
Reflected Wavefront Error (or Flatness): Flatness and Reflected Wavefront Error (RWE) are specifications that apply to dichroic beam splitters.
The Flatness is actual physical deviation of a component surface from a perfectly plane surface.
The Reflected Wavefront Error is the deviation of a wavefront reflecting off a component relative to a perfect wavefront reflecting off a perfectly plane surface.
These values are typically defined relative to a reference wavelength, peak-valley, and over a specified area such as the clear aperture (CA).
Polarization: The plane that the electric field of a light source oscillates in, typically a laser light source. Lamps and LED light sources will produce unpolarized light (an equal mixture of polarizations).
When light is incident on an optical filter at a non-normal angle of incidence, the polarization of the light can be described by two orthogonal vector components associated with the orientation of the electric field of the light wave.
The polarization component that is perpendicular to the plane of incidence is called the “s” component, and the component that is parallel to the plane of incidence is called the “p” component.
These polarization components can be used to further specify the values for Transmission and Blocking/Reflection for polarization sensitive applications.