Optical sensor for bill validation

An optical sensor for bill validation comprising:

• a pair of partitions arranged in spaced and parallel relation to each other, a bill passageway defined between the pair of the partitions, and a reflection type optical device assembled in at least one of the partitions to form a part of the bill passageway, wherein:
• the reflection type optical device has a housing for holding an optical component,
• the housing comprises a lid and a casing, the lid being formed of light-permeable materials to allow lights irradiated from the optical component and reflected on a bill to pass through the lid, and the casing enclosing the optical component in combination with the lid,
• the lid of the housing is fit in an opening of one of the partitions to make the lid form the part of the bill passageway,
• the casing comprises a casing side wall for covering side surfaces of the optical component, and a casing bottom wall for covering a bottom surface of the optical component,
• the casing bottom wall of the casing comprises a channel-shaped notch and a tongue formed by the channel-shaped notch,
• the tongue of the casing bottom wall generates its own elastic force by an elastic deformation when the optical component is mounted to forcibly urge the optical component toward the lid.