Linear Variable Dichroic –Dependence on spot-size and AOI

When using Continuously Variable Filters in your optical system it is important to take into consideration how the filter is illuminated.

This white paper analyzes the spectral performance of a 60mm long linear variable dichroic designed for 45 degrees Angle of Incidence (AOI). The study investigates the influence of light spot width and angular distribution of incident light on the dichroic. Key findings include:

1. Dependence on Light Spot Width: As the width of the light spot increases, there is a slight decrease in the steepness of the edge. However, depending on the application, wider light spots (several mm) might be acceptable.
2. Angle of Incidence (AOI) Impact: As the AOI increases, there’s a shift towards shorter wavelengths. The shape of the edge remains relatively stable between angular ranges of 37 to 53 degrees.
3. Opening Angle (OA) Influence: With even angular energy distribution, the average transmission varies based on the opening angle. The edge’s steepness reduces as the OA increases.