Patent ID: 8876409

Claim:
An optical device comprising: a light guide member; a holding member to hold the light guide member; an optical element to function according to light applied from the light guide member; a holder to hold the optical element; and an adhesive to join the holding member and the holder to each other, the holding member and the holder being engaged with each other so that the optical element is placed on an optical axis of the light guide member, at least one of the holding member and the holder having a joint structure extending along the light guide member, the joint structure forming a gap to allow the adhesive to be injected between the holding member and the holder, the holding member and the holder being joined to each other with the adhesive injected into the gap, wherein the holder has joint projections forming the joint structure; the adhesive comprises a light curing adhesive, each of the joint projections having a shape that allows light to be applied to the adhesive from surrounding of the holder without interference by the joint projections; and a sectional shape of each of the joint projections is a generally sector shape.