Abstract: An image forming device capable of detecting the presence/absence of ink as well as whether an ink tank is mounted. A detachable ink tank 32 on a carriage 31 includes a prism 32C, and a reflective optical sensor 33 detects the presence/absence of ink depending on the difference in refractive index between the two states, that is, filled with ink and empty. A reflector lever 35, movable in response to the ink tank 32 being mounted or not, is provided on the bottom of an ink tank holder 34. The reflector lever 35 has one end fixed on a lower part of the ink tank and the other end that is a free end consisting of a triangular reflector 35D. The reflector lever 35 is normally urged upward by a resilient member 35A, and it will not direct the reflection toward the sensor 33 in the absence of the ink tank whereas it is deformed in the presence/absence of the ink tank to direct the reflection toward the sensor 33. As a result, the presence/absence of the ink tank is detected.

Abstract: A media detection method and device which can detect media precisely in spite of individual variations and mechanical assembly errors of optical sensors and contamination of light emitting and receiving parts of the optical sensors, and which, even when the medium is not yet provided, can make setting for medium detection and precisely detect the medium in a short time; wherein first, a comparison reference voltage of the differential amplifier (10) is set at 0 volts and the output of the differential amplifier (10) corresponding to the output of the optical sensor (11) is determined when or where a medium is absent; by applying the output of the differential amplifier (10) to a predetermined formula, a comparison reference voltage to be given to the differential amplifier (10) during the medium detection operation is determined; next, during the actual medium detection operation, this comparison reference voltage is applied to the differential amplifier (10) and the amplifier output is compared with a predet