Patent ID: 11906731
Assignee: DISPELIX OY
Field: Optics (Instruments)
Classification: CPC G | IPC G

Claim 7:
8. The stack according to claim 7, wherein:
a first of the waveguide layers comprises a first in-coupling grating adapted to couple light to a first waveguide layer only below a first threshold wavelength,
a second of the waveguide layers comprises a second in-coupling grating adapted to couple light to a second waveguide layer only below a second threshold wavelength higher than the first threshold wavelength, and
a third waveguide layer comprises an in-coupling grating configured to couple light to a third waveguide layer above said second threshold wavelength,
the stack further comprising:
a first wavelength filter element arranged between the first and the second waveguide layer and arranged to prevent wavelengths below the first threshold wavelength entering the second in-coupling grating, and
a second wavelength filter element arranged between the second and the third waveguide layer and arranged to prevent wavelengths below the second threshold wavelength entering the third in-coupling grating.