Patent ID: 8123317

Claim:
An ink tank comprising: an ink-containing part having an inside configured to contain ink; and an optical detector configured to optically detect a presence or an absence of ink in the ink-containing part, wherein the optical detector comprises: a luminescent material; a light-reflecting part configured to reflect irradiation light irradiated from an outside of the ink-containing part onto the luminescent material, so that the luminescent material is excited by the light that has been reflected by the light-reflecting part and emits light of a wavelength that is different from a wavelength of the irradiation light; and a light-shielding part configured to shield the luminescent material from refracted light when ink is present in the ink-containing part, wherein the luminescent material receives the reflected light from the light-reflecting part and emits the light of the different wavelength when ink is absent from the ink-containing part.