How a Filter is Specified（3）

 While similar to CHA, a non-zero FOV may result from a convergent or divergent beam or a use condition in which collimated light may vary in its angle of incident over time.

Changing the AOI, CHA, or FOV of your incident light will change the spectral response of the filter. For more information on how the edge pass filters respond to changes in AOI, please review our technical note Edge Filters for Raman Spectroscopy. For a custom filter, it is important to provide the AOI and CHA/FOV ranges in order for the filter design engineer to optimize the filter to work over these ranges.

Beam size information, and in the case of a filter with a CHA, the distribution of light over the angle range (e.g. Gaussian versus flat-top) is useful when providing the functional use specifications.

Polarization:

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 is referenced to the plane of incidence (the plane defined by a vector in the direction of the beam and the normal to the surface) and contains both the incident and the reflected light rays. 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.