Patent ID: 8743461

Claim:
An optical module comprising: an interference filter including a first substrate having a first thermal expansion coefficient, a second substrate which faces the first substrate, a first reflection film which is formed on the first substrate, and a second reflection film which is formed on the second substrate and faces the first reflection film through a gap; and a fixing portion to which the first substrate of the interference filter is fixed, having a second thermal expansion coefficient which has a value different from the first thermal expansion coefficient, wherein the interference filter is fixed to the fixing portion through an adhesive layer of gel-like resin; and wherein when the thickness of the adhesive layer is Ta (mm), the linear expansion coefficient of the first substrate is α 1 (K −1 ), the Young's modulus of the first substrate is E 1 (GPa), the thickness of the first substrate is T 1 (mm), the linear expansion coefficient of the fixing portion is α 2 (K −1 ), the Young's modulus of the fixing portion is E 2 (GPa), the thickness of the fixing portion is T 2 (mm), and a coefficient based on the gel-like resin is A, the thickness of the adhesive layer satisfies the following formula (1) in a case where (α 1 ·E 1 ·T 1 2 )≦(α 2 ·E 2 ·T 2 2 ), and satisfies the following formula (2) in a case where (α 1 ·E 1 ·T 1 2 )>(a 2 ·E 2 ·T 2 2 ): Ta≧A ·(α2 ·E 2 ·T 2 2 )/(α1 ·E 1 ·T 1 2 ) (1) Ta≧A ·(α1 ·E 1 ·T 1 2 )/(α2 ·E 2 ·T 2 2 ) (2).