PURPOSE: To detect the ink residual amount of an ink tank of different color by a single light source by disposing the source at a predetermined angle to the first surface of a vessel, and providing a photodetector on an optical path of the light to be irradiated from the second surface of the vessel when the liquid volume is zero.
CONSTITUTION: Liquid volume detecting means having a photodetector 4 for detecting the wavelength of a light to be irradiated from a light source 3 is provided in an ink tank 1 having an atmosphere communication port 8 at its upper part to supply ink 2 to a recording head 5 via a supply port 7 of an ink jet recorder. In this case, if the incident point of the light to the surface of the tank 1 is higher than the liquid level of the ink 2, the source 3 is so obliquely disposed that an incident angle θ becomes θ>arcsine (1/n) (n: the refractive index of the ink) so as to allow the light to be incident to the first surface and then arrive at the second surface of the tank 1. If the liquid volume is zero, a photodetector 4 such as a CCD, etc., is disposed on the optical path of the light to be irradiated from the second surface of the tank 1.
NAGOSHI SHIGEYASU
KATO MASAO
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