Patent ID: 11927770
Assignee: SANTEC HOLDINGS CORPORATION
Field: Optics (Instruments)
Classification: CPC G | IPC G

Claim 9:
10. The tunable filter according to claim 1, wherein
the tunable filter is designed so an incidence angle α of light of a wavelength λ incident on the transmissive diffraction grating satisfies the following relational expression:

2 sin α≠Nmλ, 

where N is an inverse of a diffraction-grating period and m is a diffraction order, for an entirety of a wavelength range λ1≤λ≤λ2, from a shortest wavelength λ=λ1 to a longest wavelength λ=λ2, of the light that, as the input light, becomes incident on the transmissive diffraction grating from the optical input/output unit via the first mirror.