A light source-integrated lens assembly includes a lens including first through hole at its center along optical axis, an internal light shielding member including second through hole at its center and first protrusion that protrudes from front surface of the lens, and a light emitting element configured to emit light to target object. The internal light shielding member is fitted into the first through hole and the light emitting element is fitted into the second through hole to form a single integrated unit. The lens receives light emitted from the light emitting element and diffused and reflected from inside the target object. When the internal light shielding member is brought into contact with surface of the target object, the internal light shielding member prevents light emitted from the light emitting element and directly reflected at the surface of the target object from being incident on the lens.