Angle of Incidence in Optical Filters

Understanding Angle of Incidence

The angle of incidence (AOI) is the angle between incoming light and the optical filter’s surface normal. It’s not the angle from the light source to the filter’s center. Without collimation, light remains divergent, and the AOI is never 0°.

Impact on Interference Filters

Interference filters, like narrowband optical filters, are highly sensitive to AOI. For an 850nm narrowband filter, increasing the AOI shifts the center wavelength to shorter values. At 50°, the wavelength may drop to ~760nm, altering performance.

Placement Matters

Place filters between the lens and CCD/CMOS, where divergence angles are typically ≤12°, ensuring stable performance. Positioning filters in front of the lens exposes them to wide-angle stray light, reducing effectiveness in applications like fluorescence microscopy.

Why Choose MOVO OPTO?

MOVO OPTO’s high-precision optical filters are designed for optimal AOI performance in UV, VIS, NIR, IR, and fluorescence applications. Explore custom optical filters at www.optofilters.com, meeting global standards.