INTERFERENCE FILTER AND PHOTODETECTOR WITH INTERFERENCE FILTER

摘要

PURPOSE: To improve the transmittance of the interference filter having dielectric layers of low refractive indices and dielectric layers of high refractive indices by decreasing the ripples in the transmission band on a short wavelength side than in the non-transmission band. ;CONSTITUTION: This IR cut filter 4 consists of 25 layers provided with the low-refractive index dielectric layers 2 in the layers of the odd numbers counted from a glass substrate 1 on this glass substrate 1 and the high-refractive index dielectric layers 3 likewise in the layers of even numbers and ending with the low-refractive index dielectric layer 2 in the final layer counted from the glass substrate 1. The above-mentioned filter is so formed that the optical film thickness of the second layer counted from the glass substrate 1 is larger than λ/4, the optical film thickness of the third layer larger, than λ/4 and likewise the optical film thickness of the fourth layer larger than λ/4.;COPYRIGHT: (C)1994,JPO&Japio