Multi-band (dual, triple, quad) dichroic mirrors or filters have been mainly required for
microscopy application for a long time.
On the other hand, there were few inquiries for astronomical application before.

However, the number of inquiries on multi-band dichroic mirrors or filters for astronomy
is now increasing, especially in NIR wavelengths.
Complicated coating design and very precise control of film-thickness as designed in
all layers (often over 100 layers) are essential to achieve multi-passbands.

We succeeded in coating triple-band dichroic mirrors for the GPI (Gemini Planet Imager)
in spite of narrow passband in 2025.