A printer includes, in its fixing device operable to fix toner particles onto a recording medium, a heating roller containing magnetic metal, a fixing roller disposed parallel to the heating roller, an endless belt containing magnetic metal bridged across the heating roller and the fixing roller. The microwave energy is focused onto a device to be charged by a power transmitter having one or more adaptively-phased microwave array emitters. This method can solve the problem that in the multi-source document copy mode the background noise of all images cannot be removed at the same time in the prior art. The groove is open to ambient water, which will further reduce the friction. Further, the pixel includes a transfer transistor formed between the photodiode and a floating node and selectively operative to transfer a signal from the photodiode to the floating node.